Java tutorial
/* * Copyright (c) 2008, 2018, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.lang.invoke; import java.lang.constant.ClassDesc; import java.lang.constant.Constable; import java.lang.constant.MethodTypeDesc; import java.lang.ref.Reference; import java.lang.ref.ReferenceQueue; import java.lang.ref.WeakReference; import java.util.Arrays; import java.util.Collections; import java.util.List; import java.util.NoSuchElementException; import java.util.Objects; import java.util.Optional; import java.util.StringJoiner; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentMap; import java.util.stream.Stream; import jdk.internal.vm.annotation.Stable; import sun.invoke.util.BytecodeDescriptor; import sun.invoke.util.VerifyType; import sun.invoke.util.Wrapper; import static java.lang.invoke.MethodHandleStatics.UNSAFE; import static java.lang.invoke.MethodHandleStatics.newIllegalArgumentException; /** * A method type represents the arguments and return type accepted and * returned by a method handle, or the arguments and return type passed * and expected by a method handle caller. Method types must be properly * matched between a method handle and all its callers, * and the JVM's operations enforce this matching at, specifically * during calls to {@link MethodHandle#invokeExact MethodHandle.invokeExact} * and {@link MethodHandle#invoke MethodHandle.invoke}, and during execution * of {@code invokedynamic} instructions. * <p> * The structure is a return type accompanied by any number of parameter types. * The types (primitive, {@code void}, and reference) are represented by {@link Class} objects. * (For ease of exposition, we treat {@code void} as if it were a type. * In fact, it denotes the absence of a return type.) * <p> * All instances of {@code MethodType} are immutable. * Two instances are completely interchangeable if they compare equal. * Equality depends on pairwise correspondence of the return and parameter types and on nothing else. * <p> * This type can be created only by factory methods. * All factory methods may cache values, though caching is not guaranteed. * Some factory methods are static, while others are virtual methods which * modify precursor method types, e.g., by changing a selected parameter. * <p> * Factory methods which operate on groups of parameter types * are systematically presented in two versions, so that both Java arrays and * Java lists can be used to work with groups of parameter types. * The query methods {@code parameterArray} and {@code parameterList} * also provide a choice between arrays and lists. * <p> * {@code MethodType} objects are sometimes derived from bytecode instructions * such as {@code invokedynamic}, specifically from the type descriptor strings associated * with the instructions in a class file's constant pool. * <p> * Like classes and strings, method types can also be represented directly * in a class file's constant pool as constants. * A method type may be loaded by an {@code ldc} instruction which refers * to a suitable {@code CONSTANT_MethodType} constant pool entry. * The entry refers to a {@code CONSTANT_Utf8} spelling for the descriptor string. * (For full details on method type constants, * see sections 4.4.8 and 5.4.3.5 of the Java Virtual Machine Specification.) * <p> * When the JVM materializes a {@code MethodType} from a descriptor string, * all classes named in the descriptor must be accessible, and will be loaded. * (But the classes need not be initialized, as is the case with a {@code CONSTANT_Class}.) * This loading may occur at any time before the {@code MethodType} object is first derived. * @author John Rose, JSR 292 EG * @since 1.7 */ public final class MethodType implements Constable, TypeDescriptor.OfMethod<Class<?>, MethodType>, java.io.Serializable { private static final long serialVersionUID = 292L; // {rtype, {ptype...}} // The rtype and ptypes fields define the structural identity of the method type: private final @Stable Class<?> rtype; private final @Stable Class<?>[] ptypes; // The remaining fields are caches of various sorts: private @Stable MethodTypeForm form; // erased form, plus cached data about primitives private @Stable MethodType wrapAlt; // alternative wrapped/unwrapped version private @Stable Invokers invokers; // cache of handy higher-order adapters private @Stable String methodDescriptor; // cache for toMethodDescriptorString /** * Constructor that performs no copying or validation. * Should only be called from the factory method makeImpl */ private MethodType(Class<?> rtype, Class<?>[] ptypes) { this.rtype = rtype; this.ptypes = ptypes; } /*trusted*/ MethodTypeForm form() { return form; } /*trusted*/ Class<?> rtype() { return rtype; } /*trusted*/ Class<?>[] ptypes() { return ptypes; } void setForm(MethodTypeForm f) { form = f; } /** This number, mandated by the JVM spec as 255, * is the maximum number of <em>slots</em> * that any Java method can receive in its argument list. * It limits both JVM signatures and method type objects. * The longest possible invocation will look like * {@code staticMethod(arg1, arg2, ..., arg255)} or * {@code x.virtualMethod(arg1, arg2, ..., arg254)}. */ /*non-public*/ static final int MAX_JVM_ARITY = 255; // this is mandated by the JVM spec. /** This number is the maximum arity of a method handle, 254. * It is derived from the absolute JVM-imposed arity by subtracting one, * which is the slot occupied by the method handle itself at the * beginning of the argument list used to invoke the method handle. * The longest possible invocation will look like * {@code mh.invoke(arg1, arg2, ..., arg254)}. */ // Issue: Should we allow MH.invokeWithArguments to go to the full 255? /*non-public*/ static final int MAX_MH_ARITY = MAX_JVM_ARITY - 1; // deduct one for mh receiver /** This number is the maximum arity of a method handle invoker, 253. * It is derived from the absolute JVM-imposed arity by subtracting two, * which are the slots occupied by invoke method handle, and the * target method handle, which are both at the beginning of the argument * list used to invoke the target method handle. * The longest possible invocation will look like * {@code invokermh.invoke(targetmh, arg1, arg2, ..., arg253)}. */ /*non-public*/ static final int MAX_MH_INVOKER_ARITY = MAX_MH_ARITY - 1; // deduct one more for invoker private static void checkRtype(Class<?> rtype) { Objects.requireNonNull(rtype); } private static void checkPtype(Class<?> ptype) { Objects.requireNonNull(ptype); if (ptype == void.class) throw newIllegalArgumentException("parameter type cannot be void"); } /** Return number of extra slots (count of long/double args). */ private static int checkPtypes(Class<?>[] ptypes) { int slots = 0; for (Class<?> ptype : ptypes) { checkPtype(ptype); if (ptype == double.class || ptype == long.class) { slots++; } } checkSlotCount(ptypes.length + slots); return slots; } static { // MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work: assert ((MAX_JVM_ARITY & (MAX_JVM_ARITY + 1)) == 0); } static void checkSlotCount(int count) { if ((count & MAX_JVM_ARITY) != count) throw newIllegalArgumentException("bad parameter count " + count); } private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) { if (num instanceof Integer) num = "bad index: " + num; return new IndexOutOfBoundsException(num.toString()); } static final ConcurrentWeakInternSet<MethodType> internTable = new ConcurrentWeakInternSet<>(); static final Class<?>[] NO_PTYPES = {}; /** * Finds or creates an instance of the given method type. * @param rtype the return type * @param ptypes the parameter types * @return a method type with the given components * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class} */ public static MethodType methodType(Class<?> rtype, Class<?>[] ptypes) { return makeImpl(rtype, ptypes, false); } /** * Finds or creates a method type with the given components. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * @param rtype the return type * @param ptypes the parameter types * @return a method type with the given components * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class} */ public static MethodType methodType(Class<?> rtype, List<Class<?>> ptypes) { boolean notrust = false; // random List impl. could return evil ptypes array return makeImpl(rtype, listToArray(ptypes), notrust); } private static Class<?>[] listToArray(List<Class<?>> ptypes) { // sanity check the size before the toArray call, since size might be huge checkSlotCount(ptypes.size()); return ptypes.toArray(NO_PTYPES); } /** * Finds or creates a method type with the given components. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * The leading parameter type is prepended to the remaining array. * @param rtype the return type * @param ptype0 the first parameter type * @param ptypes the remaining parameter types * @return a method type with the given components * @throws NullPointerException if {@code rtype} or {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is null * @throws IllegalArgumentException if {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is {@code void.class} */ public static MethodType methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes) { Class<?>[] ptypes1 = new Class<?>[1 + ptypes.length]; ptypes1[0] = ptype0; System.arraycopy(ptypes, 0, ptypes1, 1, ptypes.length); return makeImpl(rtype, ptypes1, true); } /** * Finds or creates a method type with the given components. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * The resulting method has no parameter types. * @param rtype the return type * @return a method type with the given return value * @throws NullPointerException if {@code rtype} is null */ public static MethodType methodType(Class<?> rtype) { return makeImpl(rtype, NO_PTYPES, true); } /** * Finds or creates a method type with the given components. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * The resulting method has the single given parameter type. * @param rtype the return type * @param ptype0 the parameter type * @return a method type with the given return value and parameter type * @throws NullPointerException if {@code rtype} or {@code ptype0} is null * @throws IllegalArgumentException if {@code ptype0} is {@code void.class} */ public static MethodType methodType(Class<?> rtype, Class<?> ptype0) { return makeImpl(rtype, new Class<?>[] { ptype0 }, true); } /** * Finds or creates a method type with the given components. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * The resulting method has the same parameter types as {@code ptypes}, * and the specified return type. * @param rtype the return type * @param ptypes the method type which supplies the parameter types * @return a method type with the given components * @throws NullPointerException if {@code rtype} or {@code ptypes} is null */ public static MethodType methodType(Class<?> rtype, MethodType ptypes) { return makeImpl(rtype, ptypes.ptypes, true); } /** * Sole factory method to find or create an interned method type. * @param rtype desired return type * @param ptypes desired parameter types * @param trusted whether the ptypes can be used without cloning * @return the unique method type of the desired structure */ /*trusted*/ static MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) { if (ptypes.length == 0) { ptypes = NO_PTYPES; trusted = true; } MethodType primordialMT = new MethodType(rtype, ptypes); MethodType mt = internTable.get(primordialMT); if (mt != null) return mt; // promote the object to the Real Thing, and reprobe MethodType.checkRtype(rtype); if (trusted) { MethodType.checkPtypes(ptypes); mt = primordialMT; } else { // Make defensive copy then validate ptypes = Arrays.copyOf(ptypes, ptypes.length); MethodType.checkPtypes(ptypes); mt = new MethodType(rtype, ptypes); } mt.form = MethodTypeForm.findForm(mt); return internTable.add(mt); } private static final @Stable MethodType[] objectOnlyTypes = new MethodType[20]; /** * Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * All parameters and the return type will be {@code Object}, * except the final array parameter if any, which will be {@code Object[]}. * @param objectArgCount number of parameters (excluding the final array parameter if any) * @param finalArray whether there will be a trailing array parameter, of type {@code Object[]} * @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true) * @see #genericMethodType(int) */ public static MethodType genericMethodType(int objectArgCount, boolean finalArray) { MethodType mt; checkSlotCount(objectArgCount); int ivarargs = (!finalArray ? 0 : 1); int ootIndex = objectArgCount * 2 + ivarargs; if (ootIndex < objectOnlyTypes.length) { mt = objectOnlyTypes[ootIndex]; if (mt != null) return mt; } Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs]; Arrays.fill(ptypes, Object.class); if (ivarargs != 0) ptypes[objectArgCount] = Object[].class; mt = makeImpl(Object.class, ptypes, true); if (ootIndex < objectOnlyTypes.length) { objectOnlyTypes[ootIndex] = mt; // cache it here also! } return mt; } /** * Finds or creates a method type whose components are all {@code Object}. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * All parameters and the return type will be Object. * @param objectArgCount number of parameters * @return a generally applicable method type, for all calls of the given argument count * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 * @see #genericMethodType(int, boolean) */ public static MethodType genericMethodType(int objectArgCount) { return genericMethodType(objectArgCount, false); } /** * Finds or creates a method type with a single different parameter type. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * @param num the index (zero-based) of the parameter type to change * @param nptype a new parameter type to replace the old one with * @return the same type, except with the selected parameter changed * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()} * @throws IllegalArgumentException if {@code nptype} is {@code void.class} * @throws NullPointerException if {@code nptype} is null */ public MethodType changeParameterType(int num, Class<?> nptype) { if (parameterType(num) == nptype) return this; checkPtype(nptype); Class<?>[] nptypes = ptypes.clone(); nptypes[num] = nptype; return makeImpl(rtype, nptypes, true); } /** * Finds or creates a method type with additional parameter types. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * @param num the position (zero-based) of the inserted parameter type(s) * @param ptypesToInsert zero or more new parameter types to insert into the parameter list * @return the same type, except with the selected parameter(s) inserted * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()} * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} * or if the resulting method type would have more than 255 parameter slots * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null */ public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) { int len = ptypes.length; if (num < 0 || num > len) throw newIndexOutOfBoundsException(num); int ins = checkPtypes(ptypesToInsert); checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins); int ilen = ptypesToInsert.length; if (ilen == 0) return this; Class<?>[] nptypes = new Class<?>[len + ilen]; if (num > 0) { System.arraycopy(ptypes, 0, nptypes, 0, num); } System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen); if (num < len) { System.arraycopy(ptypes, num, nptypes, num + ilen, len - num); } return makeImpl(rtype, nptypes, true); } /** * Finds or creates a method type with additional parameter types. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list * @return the same type, except with the selected parameter(s) appended * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} * or if the resulting method type would have more than 255 parameter slots * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null */ public MethodType appendParameterTypes(Class<?>... ptypesToInsert) { return insertParameterTypes(parameterCount(), ptypesToInsert); } /** * Finds or creates a method type with additional parameter types. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * @param num the position (zero-based) of the inserted parameter type(s) * @param ptypesToInsert zero or more new parameter types to insert into the parameter list * @return the same type, except with the selected parameter(s) inserted * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()} * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} * or if the resulting method type would have more than 255 parameter slots * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null */ public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) { return insertParameterTypes(num, listToArray(ptypesToInsert)); } /** * Finds or creates a method type with additional parameter types. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list * @return the same type, except with the selected parameter(s) appended * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} * or if the resulting method type would have more than 255 parameter slots * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null */ public MethodType appendParameterTypes(List<Class<?>> ptypesToInsert) { return insertParameterTypes(parameterCount(), ptypesToInsert); } /** * Finds or creates a method type with modified parameter types. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * @param start the position (zero-based) of the first replaced parameter type(s) * @param end the position (zero-based) after the last replaced parameter type(s) * @param ptypesToInsert zero or more new parameter types to insert into the parameter list * @return the same type, except with the selected parameter(s) replaced * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()} * or if {@code end} is negative or greater than {@code parameterCount()} * or if {@code start} is greater than {@code end} * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} * or if the resulting method type would have more than 255 parameter slots * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null */ /*non-public*/ MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) { if (start == end) return insertParameterTypes(start, ptypesToInsert); int len = ptypes.length; if (!(0 <= start && start <= end && end <= len)) throw newIndexOutOfBoundsException("start=" + start + " end=" + end); int ilen = ptypesToInsert.length; if (ilen == 0) return dropParameterTypes(start, end); return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert); } /** Replace the last arrayLength parameter types with the component type of arrayType. * @param arrayType any array type * @param pos position at which to spread * @param arrayLength the number of parameter types to change * @return the resulting type */ /*non-public*/ MethodType asSpreaderType(Class<?> arrayType, int pos, int arrayLength) { assert (parameterCount() >= arrayLength); int spreadPos = pos; if (arrayLength == 0) return this; // nothing to change if (arrayType == Object[].class) { if (isGeneric()) return this; // nothing to change if (spreadPos == 0) { // no leading arguments to preserve; go generic MethodType res = genericMethodType(arrayLength); if (rtype != Object.class) { res = res.changeReturnType(rtype); } return res; } } Class<?> elemType = arrayType.getComponentType(); assert (elemType != null); for (int i = spreadPos; i < spreadPos + arrayLength; i++) { if (ptypes[i] != elemType) { Class<?>[] fixedPtypes = ptypes.clone(); Arrays.fill(fixedPtypes, i, spreadPos + arrayLength, elemType); return methodType(rtype, fixedPtypes); } } return this; // arguments check out; no change } /** Return the leading parameter type, which must exist and be a reference. * @return the leading parameter type, after error checks */ /*non-public*/ Class<?> leadingReferenceParameter() { Class<?> ptype; if (ptypes.length == 0 || (ptype = ptypes[0]).isPrimitive()) throw newIllegalArgumentException("no leading reference parameter"); return ptype; } /** Delete the last parameter type and replace it with arrayLength copies of the component type of arrayType. * @param arrayType any array type * @param pos position at which to insert parameters * @param arrayLength the number of parameter types to insert * @return the resulting type */ /*non-public*/ MethodType asCollectorType(Class<?> arrayType, int pos, int arrayLength) { assert (parameterCount() >= 1); assert (pos < ptypes.length); assert (ptypes[pos].isAssignableFrom(arrayType)); MethodType res; if (arrayType == Object[].class) { res = genericMethodType(arrayLength); if (rtype != Object.class) { res = res.changeReturnType(rtype); } } else { Class<?> elemType = arrayType.getComponentType(); assert (elemType != null); res = methodType(rtype, Collections.nCopies(arrayLength, elemType)); } if (ptypes.length == 1) { return res; } else { // insert after (if need be), then before if (pos < ptypes.length - 1) { res = res.insertParameterTypes(arrayLength, Arrays.copyOfRange(ptypes, pos + 1, ptypes.length)); } return res.insertParameterTypes(0, Arrays.copyOf(ptypes, pos)); } } /** * Finds or creates a method type with some parameter types omitted. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * @param start the index (zero-based) of the first parameter type to remove * @param end the index (greater than {@code start}) of the first parameter type after not to remove * @return the same type, except with the selected parameter(s) removed * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()} * or if {@code end} is negative or greater than {@code parameterCount()} * or if {@code start} is greater than {@code end} */ public MethodType dropParameterTypes(int start, int end) { int len = ptypes.length; if (!(0 <= start && start <= end && end <= len)) throw newIndexOutOfBoundsException("start=" + start + " end=" + end); if (start == end) return this; Class<?>[] nptypes; if (start == 0) { if (end == len) { // drop all parameters nptypes = NO_PTYPES; } else { // drop initial parameter(s) nptypes = Arrays.copyOfRange(ptypes, end, len); } } else { if (end == len) { // drop trailing parameter(s) nptypes = Arrays.copyOfRange(ptypes, 0, start); } else { int tail = len - end; nptypes = Arrays.copyOfRange(ptypes, 0, start + tail); System.arraycopy(ptypes, end, nptypes, start, tail); } } return makeImpl(rtype, nptypes, true); } /** * Finds or creates a method type with a different return type. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * @param nrtype a return parameter type to replace the old one with * @return the same type, except with the return type change * @throws NullPointerException if {@code nrtype} is null */ public MethodType changeReturnType(Class<?> nrtype) { if (returnType() == nrtype) return this; return makeImpl(nrtype, ptypes, true); } /** * Reports if this type contains a primitive argument or return value. * The return type {@code void} counts as a primitive. * @return true if any of the types are primitives */ public boolean hasPrimitives() { return form.hasPrimitives(); } /** * Reports if this type contains a wrapper argument or return value. * Wrappers are types which box primitive values, such as {@link Integer}. * The reference type {@code java.lang.Void} counts as a wrapper, * if it occurs as a return type. * @return true if any of the types are wrappers */ public boolean hasWrappers() { return unwrap() != this; } /** * Erases all reference types to {@code Object}. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * All primitive types (including {@code void}) will remain unchanged. * @return a version of the original type with all reference types replaced */ public MethodType erase() { return form.erasedType(); } /** * Erases all reference types to {@code Object}, and all subword types to {@code int}. * This is the reduced type polymorphism used by private methods * such as {@link MethodHandle#invokeBasic invokeBasic}. * @return a version of the original type with all reference and subword types replaced */ /*non-public*/ MethodType basicType() { return form.basicType(); } private static final @Stable Class<?>[] METHOD_HANDLE_ARRAY = new Class<?>[] { MethodHandle.class }; /** * @return a version of the original type with MethodHandle prepended as the first argument */ /*non-public*/ MethodType invokerType() { return insertParameterTypes(0, METHOD_HANDLE_ARRAY); } /** * Converts all types, both reference and primitive, to {@code Object}. * Convenience method for {@link #genericMethodType(int) genericMethodType}. * The expression {@code type.wrap().erase()} produces the same value * as {@code type.generic()}. * @return a version of the original type with all types replaced */ public MethodType generic() { return genericMethodType(parameterCount()); } /*non-public*/ boolean isGeneric() { return this == erase() && !hasPrimitives(); } /** * Converts all primitive types to their corresponding wrapper types. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * All reference types (including wrapper types) will remain unchanged. * A {@code void} return type is changed to the type {@code java.lang.Void}. * The expression {@code type.wrap().erase()} produces the same value * as {@code type.generic()}. * @return a version of the original type with all primitive types replaced */ public MethodType wrap() { return hasPrimitives() ? wrapWithPrims(this) : this; } /** * Converts all wrapper types to their corresponding primitive types. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * All primitive types (including {@code void}) will remain unchanged. * A return type of {@code java.lang.Void} is changed to {@code void}. * @return a version of the original type with all wrapper types replaced */ public MethodType unwrap() { MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this); return unwrapWithNoPrims(noprims); } private static MethodType wrapWithPrims(MethodType pt) { assert (pt.hasPrimitives()); MethodType wt = pt.wrapAlt; if (wt == null) { // fill in lazily wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP, MethodTypeForm.WRAP); assert (wt != null); pt.wrapAlt = wt; } return wt; } private static MethodType unwrapWithNoPrims(MethodType wt) { assert (!wt.hasPrimitives()); MethodType uwt = wt.wrapAlt; if (uwt == null) { // fill in lazily uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP, MethodTypeForm.UNWRAP); if (uwt == null) uwt = wt; // type has no wrappers or prims at all wt.wrapAlt = uwt; } return uwt; } /** * Returns the parameter type at the specified index, within this method type. * @param num the index (zero-based) of the desired parameter type * @return the selected parameter type * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()} */ public Class<?> parameterType(int num) { return ptypes[num]; } /** * Returns the number of parameter types in this method type. * @return the number of parameter types */ public int parameterCount() { return ptypes.length; } /** * Returns the return type of this method type. * @return the return type */ public Class<?> returnType() { return rtype; } /** * Presents the parameter types as a list (a convenience method). * The list will be immutable. * @return the parameter types (as an immutable list) */ public List<Class<?>> parameterList() { return Collections.unmodifiableList(Arrays.asList(ptypes.clone())); } /** * Returns the last parameter type of this method type. * If this type has no parameters, the sentinel value * {@code void.class} is returned instead. * @apiNote * <p> * The sentinel value is chosen so that reflective queries can be * made directly against the result value. * The sentinel value cannot be confused with a real parameter, * since {@code void} is never acceptable as a parameter type. * For variable arity invocation modes, the expression * {@link Class#getComponentType lastParameterType().getComponentType()} * is useful to query the type of the "varargs" parameter. * @return the last parameter type if any, else {@code void.class} * @since 10 */ public Class<?> lastParameterType() { int len = ptypes.length; return len == 0 ? void.class : ptypes[len - 1]; } /** * Presents the parameter types as an array (a convenience method). * Changes to the array will not result in changes to the type. * @return the parameter types (as a fresh copy if necessary) */ public Class<?>[] parameterArray() { return ptypes.clone(); } /** * Compares the specified object with this type for equality. * That is, it returns {@code true} if and only if the specified object * is also a method type with exactly the same parameters and return type. * @param x object to compare * @see Object#equals(Object) */ // This implementation may also return true if x is a WeakEntry containing // a method type that is equal to this. This is an internal implementation // detail to allow for faster method type lookups. // See ConcurrentWeakInternSet.WeakEntry#equals(Object) @Override public boolean equals(Object x) { if (this == x) { return true; } if (x instanceof MethodType) { return equals((MethodType) x); } if (x instanceof ConcurrentWeakInternSet.WeakEntry) { Object o = ((ConcurrentWeakInternSet.WeakEntry) x).get(); if (o instanceof MethodType) { return equals((MethodType) o); } } return false; } private boolean equals(MethodType that) { return this.rtype == that.rtype && Arrays.equals(this.ptypes, that.ptypes); } /** * Returns the hash code value for this method type. * It is defined to be the same as the hashcode of a List * whose elements are the return type followed by the * parameter types. * @return the hash code value for this method type * @see Object#hashCode() * @see #equals(Object) * @see List#hashCode() */ @Override public int hashCode() { int hashCode = 31 + rtype.hashCode(); for (Class<?> ptype : ptypes) hashCode = 31 * hashCode + ptype.hashCode(); return hashCode; } /** * Returns a string representation of the method type, * of the form {@code "(PT0,PT1...)RT"}. * The string representation of a method type is a * parenthesis enclosed, comma separated list of type names, * followed immediately by the return type. * <p> * Each type is represented by its * {@link java.lang.Class#getSimpleName simple name}. */ @Override public String toString() { StringJoiner sj = new StringJoiner(",", "(", ")" + rtype.getSimpleName()); for (int i = 0; i < ptypes.length; i++) { sj.add(ptypes[i].getSimpleName()); } return sj.toString(); } /** True if my parameter list is effectively identical to the given full list, * after skipping the given number of my own initial parameters. * In other words, after disregarding {@code skipPos} parameters, * my remaining parameter list is no longer than the {@code fullList}, and * is equal to the same-length initial sublist of {@code fullList}. */ /*non-public*/ boolean effectivelyIdenticalParameters(int skipPos, List<Class<?>> fullList) { int myLen = ptypes.length, fullLen = fullList.size(); if (skipPos > myLen || myLen - skipPos > fullLen) return false; List<Class<?>> myList = Arrays.asList(ptypes); if (skipPos != 0) { myList = myList.subList(skipPos, myLen); myLen -= skipPos; } if (fullLen == myLen) return myList.equals(fullList); else return myList.equals(fullList.subList(0, myLen)); } /** True if the old return type can always be viewed (w/o casting) under new return type, * and the new parameters can be viewed (w/o casting) under the old parameter types. */ /*non-public*/ boolean isViewableAs(MethodType newType, boolean keepInterfaces) { if (!VerifyType.isNullConversion(returnType(), newType.returnType(), keepInterfaces)) return false; if (form == newType.form && form.erasedType == this) return true; // my reference parameters are all Object if (ptypes == newType.ptypes) return true; int argc = parameterCount(); if (argc != newType.parameterCount()) return false; for (int i = 0; i < argc; i++) { if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i), keepInterfaces)) return false; } return true; } /*non-public*/ boolean isConvertibleTo(MethodType newType) { MethodTypeForm oldForm = this.form(); MethodTypeForm newForm = newType.form(); if (oldForm == newForm) // same parameter count, same primitive/object mix return true; if (!canConvert(returnType(), newType.returnType())) return false; Class<?>[] srcTypes = newType.ptypes; Class<?>[] dstTypes = ptypes; if (srcTypes == dstTypes) return true; int argc; if ((argc = srcTypes.length) != dstTypes.length) return false; if (argc <= 1) { if (argc == 1 && !canConvert(srcTypes[0], dstTypes[0])) return false; return true; } if ((oldForm.primitiveParameterCount() == 0 && oldForm.erasedType == this) || (newForm.primitiveParameterCount() == 0 && newForm.erasedType == newType)) { // Somewhat complicated test to avoid a loop of 2 or more trips. // If either type has only Object parameters, we know we can convert. assert (canConvertParameters(srcTypes, dstTypes)); return true; } return canConvertParameters(srcTypes, dstTypes); } /** Returns true if MHs.explicitCastArguments produces the same result as MH.asType. * If the type conversion is impossible for either, the result should be false. */ /*non-public*/ boolean explicitCastEquivalentToAsType(MethodType newType) { if (this == newType) return true; if (!explicitCastEquivalentToAsType(rtype, newType.rtype)) { return false; } Class<?>[] srcTypes = newType.ptypes; Class<?>[] dstTypes = ptypes; if (dstTypes == srcTypes) { return true; } assert (dstTypes.length == srcTypes.length); for (int i = 0; i < dstTypes.length; i++) { if (!explicitCastEquivalentToAsType(srcTypes[i], dstTypes[i])) { return false; } } return true; } /** Reports true if the src can be converted to the dst, by both asType and MHs.eCE, * and with the same effect. * MHs.eCA has the following "upgrades" to MH.asType: * 1. interfaces are unchecked (that is, treated as if aliased to Object) * Therefore, {@code Object->CharSequence} is possible in both cases but has different semantics * 2. the full matrix of primitive-to-primitive conversions is supported * Narrowing like {@code long->byte} and basic-typing like {@code boolean->int} * are not supported by asType, but anything supported by asType is equivalent * with MHs.eCE. * 3a. unboxing conversions can be followed by the full matrix of primitive conversions * 3b. unboxing of null is permitted (creates a zero primitive value) * Other than interfaces, reference-to-reference conversions are the same. * Boxing primitives to references is the same for both operators. */ private static boolean explicitCastEquivalentToAsType(Class<?> src, Class<?> dst) { if (src == dst || dst == Object.class || dst == void.class) return true; if (src.isPrimitive()) { // Could be a prim/prim conversion, where casting is a strict superset. // Or a boxing conversion, which is always to an exact wrapper class. return canConvert(src, dst); } else if (dst.isPrimitive()) { // Unboxing behavior is different between MHs.eCA & MH.asType (see 3b). return false; } else { // R->R always works, but we have to avoid a check-cast to an interface. return !dst.isInterface() || dst.isAssignableFrom(src); } } private boolean canConvertParameters(Class<?>[] srcTypes, Class<?>[] dstTypes) { for (int i = 0; i < srcTypes.length; i++) { if (!canConvert(srcTypes[i], dstTypes[i])) { return false; } } return true; } /*non-public*/ static boolean canConvert(Class<?> src, Class<?> dst) { // short-circuit a few cases: if (src == dst || src == Object.class || dst == Object.class) return true; // the remainder of this logic is documented in MethodHandle.asType if (src.isPrimitive()) { // can force void to an explicit null, a la reflect.Method.invoke // can also force void to a primitive zero, by analogy if (src == void.class) return true; //or !dst.isPrimitive()? Wrapper sw = Wrapper.forPrimitiveType(src); if (dst.isPrimitive()) { // P->P must widen return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw); } else { // P->R must box and widen return dst.isAssignableFrom(sw.wrapperType()); } } else if (dst.isPrimitive()) { // any value can be dropped if (dst == void.class) return true; Wrapper dw = Wrapper.forPrimitiveType(dst); // R->P must be able to unbox (from a dynamically chosen type) and widen // For example: // Byte/Number/Comparable/Object -> dw:Byte -> byte. // Character/Comparable/Object -> dw:Character -> char // Boolean/Comparable/Object -> dw:Boolean -> boolean // This means that dw must be cast-compatible with src. if (src.isAssignableFrom(dw.wrapperType())) { return true; } // The above does not work if the source reference is strongly typed // to a wrapper whose primitive must be widened. For example: // Byte -> unbox:byte -> short/int/long/float/double // Character -> unbox:char -> int/long/float/double if (Wrapper.isWrapperType(src) && dw.isConvertibleFrom(Wrapper.forWrapperType(src))) { // can unbox from src and then widen to dst return true; } // We have already covered cases which arise due to runtime unboxing // of a reference type which covers several wrapper types: // Object -> cast:Integer -> unbox:int -> long/float/double // Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double // An marginal case is Number -> dw:Character -> char, which would be OK if there were a // subclass of Number which wraps a value that can convert to char. // Since there is none, we don't need an extra check here to cover char or boolean. return false; } else { // R->R always works, since null is always valid dynamically return true; } } /// Queries which have to do with the bytecode architecture /** Reports the number of JVM stack slots required to invoke a method * of this type. Note that (for historical reasons) the JVM requires * a second stack slot to pass long and double arguments. * So this method returns {@link #parameterCount() parameterCount} plus the * number of long and double parameters (if any). * <p> * This method is included for the benefit of applications that must * generate bytecodes that process method handles and invokedynamic. * @return the number of JVM stack slots for this type's parameters */ /*non-public*/ int parameterSlotCount() { return form.parameterSlotCount(); } /*non-public*/ Invokers invokers() { Invokers inv = invokers; if (inv != null) return inv; invokers = inv = new Invokers(this); return inv; } /** Reports the number of JVM stack slots which carry all parameters including and after * the given position, which must be in the range of 0 to * {@code parameterCount} inclusive. Successive parameters are * more shallowly stacked, and parameters are indexed in the bytecodes * according to their trailing edge. Thus, to obtain the depth * in the outgoing call stack of parameter {@code N}, obtain * the {@code parameterSlotDepth} of its trailing edge * at position {@code N+1}. * <p> * Parameters of type {@code long} and {@code double} occupy * two stack slots (for historical reasons) and all others occupy one. * Therefore, the number returned is the number of arguments * <em>including</em> and <em>after</em> the given parameter, * <em>plus</em> the number of long or double arguments * at or after the argument for the given parameter. * <p> * This method is included for the benefit of applications that must * generate bytecodes that process method handles and invokedynamic. * @param num an index (zero-based, inclusive) within the parameter types * @return the index of the (shallowest) JVM stack slot transmitting the * given parameter * @throws IllegalArgumentException if {@code num} is negative or greater than {@code parameterCount()} */ /*non-public*/ int parameterSlotDepth(int num) { if (num < 0 || num > ptypes.length) parameterType(num); // force a range check return form.parameterToArgSlot(num - 1); } /** Reports the number of JVM stack slots required to receive a return value * from a method of this type. * If the {@link #returnType() return type} is void, it will be zero, * else if the return type is long or double, it will be two, else one. * <p> * This method is included for the benefit of applications that must * generate bytecodes that process method handles and invokedynamic. * @return the number of JVM stack slots (0, 1, or 2) for this type's return value * Will be removed for PFD. */ /*non-public*/ int returnSlotCount() { return form.returnSlotCount(); } /** * Finds or creates an instance of a method type, given the spelling of its bytecode descriptor. * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. * Any class or interface name embedded in the descriptor string * will be resolved by calling {@link ClassLoader#loadClass(java.lang.String)} * on the given loader (or if it is null, on the system class loader). * <p> * Note that it is possible to encounter method types which cannot be * constructed by this method, because their component types are * not all reachable from a common class loader. * <p> * This method is included for the benefit of applications that must * generate bytecodes that process method handles and {@code invokedynamic}. * @param descriptor a bytecode-level type descriptor string "(T...)T" * @param loader the class loader in which to look up the types * @return a method type matching the bytecode-level type descriptor * @throws NullPointerException if the string is null * @throws IllegalArgumentException if the string is not well-formed * @throws TypeNotPresentException if a named type cannot be found */ public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader) throws IllegalArgumentException, TypeNotPresentException { return fromDescriptor(descriptor, (loader == null) ? ClassLoader.getSystemClassLoader() : loader); } /** * Same as {@link #fromMethodDescriptorString(String, ClassLoader)}, but * {@code null} ClassLoader means the bootstrap loader is used here. * <p> * IMPORTANT: This method is preferable for JDK internal use as it more * correctly interprets {@code null} ClassLoader than * {@link #fromMethodDescriptorString(String, ClassLoader)}. * Use of this method also avoids early initialization issues when system * ClassLoader is not initialized yet. */ static MethodType fromDescriptor(String descriptor, ClassLoader loader) throws IllegalArgumentException, TypeNotPresentException { if (!descriptor.startsWith("(") || // also generates NPE if needed descriptor.indexOf(')') < 0 || descriptor.indexOf('.') >= 0) throw newIllegalArgumentException("not a method descriptor: " + descriptor); List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader); Class<?> rtype = types.remove(types.size() - 1); Class<?>[] ptypes = listToArray(types); return makeImpl(rtype, ptypes, true); } /** * Produces a bytecode descriptor representation of the method type. * <p> * Note that this is not a strict inverse of {@link #fromMethodDescriptorString fromMethodDescriptorString}. * Two distinct classes which share a common name but have different class loaders * will appear identical when viewed within descriptor strings. * <p> * This method is included for the benefit of applications that must * generate bytecodes that process method handles and {@code invokedynamic}. * {@link #fromMethodDescriptorString(java.lang.String, java.lang.ClassLoader) fromMethodDescriptorString}, * because the latter requires a suitable class loader argument. * @return the bytecode type descriptor representation */ public String toMethodDescriptorString() { String desc = methodDescriptor; if (desc == null) { desc = BytecodeDescriptor.unparseMethod(this.rtype, this.ptypes); methodDescriptor = desc; } return desc; } /** * Return a field type descriptor string for this type * * @return the descriptor string * @jvms 4.3.2 Field Descriptors * @since 12 */ @Override public String descriptorString() { return toMethodDescriptorString(); } /*non-public*/ static String toFieldDescriptorString(Class<?> cls) { return BytecodeDescriptor.unparse(cls); } /** * Return a nominal descriptor for this instance, if one can be * constructed, or an empty {@link Optional} if one cannot be. * * @return An {@link Optional} containing the resulting nominal descriptor, * or an empty {@link Optional} if one cannot be constructed. * @since 12 */ @Override public Optional<MethodTypeDesc> describeConstable() { try { return Optional.of(MethodTypeDesc.of(returnType().describeConstable().orElseThrow(), Stream .of(parameterArray()).map(p -> p.describeConstable().orElseThrow()).toArray(ClassDesc[]::new))); } catch (NoSuchElementException e) { return Optional.empty(); } } /// Serialization. /** * There are no serializable fields for {@code MethodType}. */ private static final java.io.ObjectStreamField[] serialPersistentFields = {}; /** * Save the {@code MethodType} instance to a stream. * * @serialData * For portability, the serialized format does not refer to named fields. * Instead, the return type and parameter type arrays are written directly * from the {@code writeObject} method, using two calls to {@code s.writeObject} * as follows: * <blockquote><pre>{@code s.writeObject(this.returnType()); s.writeObject(this.parameterArray()); * }</pre></blockquote> * <p> * The deserialized field values are checked as if they were * provided to the factory method {@link #methodType(Class,Class[]) methodType}. * For example, null values, or {@code void} parameter types, * will lead to exceptions during deserialization. * @param s the stream to write the object to * @throws java.io.IOException if there is a problem writing the object */ private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException { s.defaultWriteObject(); // requires serialPersistentFields to be an empty array s.writeObject(returnType()); s.writeObject(parameterArray()); } /** * Reconstitute the {@code MethodType} instance from a stream (that is, * deserialize it). * This instance is a scratch object with bogus final fields. * It provides the parameters to the factory method called by * {@link #readResolve readResolve}. * After that call it is discarded. * @param s the stream to read the object from * @throws java.io.IOException if there is a problem reading the object * @throws ClassNotFoundException if one of the component classes cannot be resolved * @see #readResolve * @see #writeObject */ private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException { // Assign temporary defaults in case this object escapes MethodType_init(void.class, NO_PTYPES); s.defaultReadObject(); // requires serialPersistentFields to be an empty array Class<?> returnType = (Class<?>) s.readObject(); Class<?>[] parameterArray = (Class<?>[]) s.readObject(); parameterArray = parameterArray.clone(); // make sure it is unshared // Assign deserialized values MethodType_init(returnType, parameterArray); } // Initialization of state for deserialization only private void MethodType_init(Class<?> rtype, Class<?>[] ptypes) { // In order to communicate these values to readResolve, we must // store them into the implementation-specific final fields. checkRtype(rtype); checkPtypes(ptypes); UNSAFE.putReference(this, OffsetHolder.rtypeOffset, rtype); UNSAFE.putReference(this, OffsetHolder.ptypesOffset, ptypes); } // Support for resetting final fields while deserializing. Implement Holder // pattern to make the rarely needed offset calculation lazy. private static class OffsetHolder { static final long rtypeOffset = UNSAFE.objectFieldOffset(MethodType.class, "rtype"); static final long ptypesOffset = UNSAFE.objectFieldOffset(MethodType.class, "ptypes"); } /** * Resolves and initializes a {@code MethodType} object * after serialization. * @return the fully initialized {@code MethodType} object */ private Object readResolve() { // Do not use a trusted path for deserialization: // return makeImpl(rtype, ptypes, true); // Verify all operands, and make sure ptypes is unshared: try { return methodType(rtype, ptypes); } finally { // Re-assign defaults in case this object escapes MethodType_init(void.class, NO_PTYPES); } } /** * Simple implementation of weak concurrent intern set. * * @param <T> interned type */ private static class ConcurrentWeakInternSet<T> { private final ConcurrentMap<WeakEntry<T>, WeakEntry<T>> map; private final ReferenceQueue<T> stale; public ConcurrentWeakInternSet() { this.map = new ConcurrentHashMap<>(512); this.stale = new ReferenceQueue<>(); } /** * Get the existing interned element. * This method returns null if no element is interned. * * @param elem element to look up * @return the interned element */ public T get(T elem) { if (elem == null) throw new NullPointerException(); expungeStaleElements(); WeakEntry<T> value = map.get(elem); if (value != null) { T res = value.get(); if (res != null) { return res; } } return null; } /** * Interns the element. * Always returns non-null element, matching the one in the intern set. * Under the race against another add(), it can return <i>different</i> * element, if another thread beats us to interning it. * * @param elem element to add * @return element that was actually added */ public T add(T elem) { if (elem == null) throw new NullPointerException(); // Playing double race here, and so spinloop is required. // First race is with two concurrent updaters. // Second race is with GC purging weak ref under our feet. // Hopefully, we almost always end up with a single pass. T interned; WeakEntry<T> e = new WeakEntry<>(elem, stale); do { expungeStaleElements(); WeakEntry<T> exist = map.putIfAbsent(e, e); interned = (exist == null) ? elem : exist.get(); } while (interned == null); return interned; } private void expungeStaleElements() { Reference<? extends T> reference; while ((reference = stale.poll()) != null) { map.remove(reference); } } private static class WeakEntry<T> extends WeakReference<T> { public final int hashcode; public WeakEntry(T key, ReferenceQueue<T> queue) { super(key, queue); hashcode = key.hashCode(); } /** * This implementation returns {@code true} if {@code obj} is another * {@code WeakEntry} whose referent is equals to this referent, or * if {@code obj} is equals to the referent of this. This allows * lookups to be made without wrapping in a {@code WeakEntry}. * * @param obj the object to compare * @return true if {@code obj} is equals to this or the referent of this * @see MethodType#equals(Object) * @see Object#equals(Object) */ @Override public boolean equals(Object obj) { Object mine = get(); if (obj instanceof WeakEntry) { Object that = ((WeakEntry) obj).get(); return (that == null || mine == null) ? (this == obj) : mine.equals(that); } return (mine == null) ? (obj == null) : mine.equals(obj); } @Override public int hashCode() { return hashcode; } } } }