Java tutorial
/* * NOTICE: THE FILE HAS BEEN MODIFIED TO SUIT THE NEEDS OF THE PROJECT. * * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.robobinding.util; import java.util.HashMap; import java.util.Map; /** * Migrated some of methods from {@link org.apache.commons.lang3.ClassUtils}. * * @since 1.0 * @version $Revision: 1.0 $ * @author Cheng Wei */ public class ClassUtils { /** * Maps primitive {@code Class}es to their corresponding wrapper * {@code Class}. */ private static final Map<Class<?>, Class<?>> PRIMITIVE_WRAPPER_MAP = new HashMap<Class<?>, Class<?>>(); static { PRIMITIVE_WRAPPER_MAP.put(Boolean.TYPE, Boolean.class); PRIMITIVE_WRAPPER_MAP.put(Byte.TYPE, Byte.class); PRIMITIVE_WRAPPER_MAP.put(Character.TYPE, Character.class); PRIMITIVE_WRAPPER_MAP.put(Short.TYPE, Short.class); PRIMITIVE_WRAPPER_MAP.put(Integer.TYPE, Integer.class); PRIMITIVE_WRAPPER_MAP.put(Long.TYPE, Long.class); PRIMITIVE_WRAPPER_MAP.put(Double.TYPE, Double.class); PRIMITIVE_WRAPPER_MAP.put(Float.TYPE, Float.class); PRIMITIVE_WRAPPER_MAP.put(Void.TYPE, Void.TYPE); } /** * Maps wrapper {@code Class}es to their corresponding primitive types. */ private static final Map<Class<?>, Class<?>> WRAPPER_PRIMITIVE_MAP = new HashMap<Class<?>, Class<?>>(); static { for (final Class<?> primitiveClass : PRIMITIVE_WRAPPER_MAP.keySet()) { final Class<?> wrapperClass = PRIMITIVE_WRAPPER_MAP.get(primitiveClass); if (!primitiveClass.equals(wrapperClass)) { WRAPPER_PRIMITIVE_MAP.put(wrapperClass, primitiveClass); } } } private ClassUtils() { } /** * <p> * Checks if an array of Classes can be assigned to another array of * Classes. * </p> * * <p> * This method calls {@link #isAssignable(Class, Class) isAssignable} for * each Class pair in the input arrays. It can be used to check if a set of * arguments (the first parameter) are suitably compatible with a set of * method parameter types (the second parameter). * </p> * * <p> * Unlike the {@link Class#isAssignableFrom(java.lang.Class)} method, this * method takes into account widenings of primitive classes and {@code null} * s. * </p> * * <p> * Primitive widenings allow an int to be assigned to a {@code long}, * {@code float} or {@code double}. This method returns the correct result * for these cases. * </p> * * <p> * {@code Null} may be assigned to any reference type. This method will * return {@code true} if {@code null} is passed in and the toClass is * non-primitive. * </p> * * <p> * Specifically, this method tests whether the type represented by the * specified {@code Class} parameter can be converted to the type * represented by this {@code Class} object via an identity conversion * widening primitive or widening reference conversion. See * <em><a href="http://docs.oracle.com/javase/specs/">The Java Language Specification</a></em> * , sections 5.1.1, 5.1.2 and 5.1.4 for details. * </p> * * @param classArray * the array of Classes to check, may be {@code null} * @param toClassArray * the array of Classes to try to assign into, may be * {@code null} * @param autoboxing * whether to use implicit autoboxing/unboxing between primitives * and wrappers * @return {@code true} if assignment possible */ public static boolean isAssignable(Class<?>[] classArray, Class<?>[] toClassArray, final boolean autoboxing) { if (ArrayUtils.isSameLength(classArray, toClassArray) == false) { return false; } if (classArray == null) { classArray = ArrayUtils.EMPTY_CLASS_ARRAY; } if (toClassArray == null) { toClassArray = ArrayUtils.EMPTY_CLASS_ARRAY; } for (int i = 0; i < classArray.length; i++) { if (isAssignable(classArray[i], toClassArray[i], autoboxing) == false) { return false; } } return true; } /** * <p> * Checks if one {@code Class} can be assigned to a variable of another * {@code Class}. * </p> * * <p> * Unlike the {@link Class#isAssignableFrom(java.lang.Class)} method, this * method takes into account widenings of primitive classes and {@code null} * s. * </p> * * <p> * Primitive widenings allow an int to be assigned to a long, float or * double. This method returns the correct result for these cases. * </p> * * <p> * {@code Null} may be assigned to any reference type. This method will * return {@code true} if {@code null} is passed in and the toClass is * non-primitive. * </p> * * <p> * Specifically, this method tests whether the type represented by the * specified {@code Class} parameter can be converted to the type * represented by this {@code Class} object via an identity conversion * widening primitive or widening reference conversion. See * <em><a href="http://docs.oracle.com/javase/specs/">The Java Language Specification</a></em> * , sections 5.1.1, 5.1.2 and 5.1.4 for details. * </p> * * <p> * <strong>Since Lang 3.0,</strong> this method will default behavior for * calculating assignability between primitive and wrapper types * <em>corresponding * to the running Java version</em>; i.e. autoboxing will be the default * behavior in VMs running Java versions >= 1.5. * </p> * * @param cls * the Class to check, may be null * @param toClass * the Class to try to assign into, returns false if null * @return {@code true} if assignment possible */ public static boolean isAssignable(final Class<?> cls, final Class<?> toClass) { return isAssignable(cls, toClass, SystemUtils.isJavaVersionAtLeast(JavaVersion.JAVA_1_5)); } /** * <p> * Checks if one {@code Class} can be assigned to a variable of another * {@code Class}. * </p> * * <p> * Unlike the {@link Class#isAssignableFrom(java.lang.Class)} method, this * method takes into account widenings of primitive classes and {@code null} * s. * </p> * * <p> * Primitive widenings allow an int to be assigned to a long, float or * double. This method returns the correct result for these cases. * </p> * * <p> * {@code Null} may be assigned to any reference type. This method will * return {@code true} if {@code null} is passed in and the toClass is * non-primitive. * </p> * * <p> * Specifically, this method tests whether the type represented by the * specified {@code Class} parameter can be converted to the type * represented by this {@code Class} object via an identity conversion * widening primitive or widening reference conversion. See * <em><a href="http://docs.oracle.com/javase/specs/">The Java Language Specification</a></em> * , sections 5.1.1, 5.1.2 and 5.1.4 for details. * </p> * * @param cls * the Class to check, may be null * @param toClass * the Class to try to assign into, returns false if null * @param autoboxing * whether to use implicit autoboxing/unboxing between primitives * and wrappers * @return {@code true} if assignment possible */ public static boolean isAssignable(Class<?> cls, final Class<?> toClass, final boolean autoboxing) { if (toClass == null) { return false; } // have to check for null, as isAssignableFrom doesn't if (cls == null) { return !toClass.isPrimitive(); } // autoboxing: if (autoboxing) { if (cls.isPrimitive() && !toClass.isPrimitive()) { cls = primitiveToWrapper(cls); if (cls == null) { return false; } } if (toClass.isPrimitive() && !cls.isPrimitive()) { cls = wrapperToPrimitive(cls); if (cls == null) { return false; } } } if (cls.equals(toClass)) { return true; } if (cls.isPrimitive()) { if (toClass.isPrimitive() == false) { return false; } if (Integer.TYPE.equals(cls)) { return Long.TYPE.equals(toClass) || Float.TYPE.equals(toClass) || Double.TYPE.equals(toClass); } if (Long.TYPE.equals(cls)) { return Float.TYPE.equals(toClass) || Double.TYPE.equals(toClass); } if (Boolean.TYPE.equals(cls)) { return false; } if (Double.TYPE.equals(cls)) { return false; } if (Float.TYPE.equals(cls)) { return Double.TYPE.equals(toClass); } if (Character.TYPE.equals(cls)) { return Integer.TYPE.equals(toClass) || Long.TYPE.equals(toClass) || Float.TYPE.equals(toClass) || Double.TYPE.equals(toClass); } if (Short.TYPE.equals(cls)) { return Integer.TYPE.equals(toClass) || Long.TYPE.equals(toClass) || Float.TYPE.equals(toClass) || Double.TYPE.equals(toClass); } if (Byte.TYPE.equals(cls)) { return Short.TYPE.equals(toClass) || Integer.TYPE.equals(toClass) || Long.TYPE.equals(toClass) || Float.TYPE.equals(toClass) || Double.TYPE.equals(toClass); } // should never get here return false; } return toClass.isAssignableFrom(cls); } /** * <p> * Converts the specified primitive Class object to its corresponding * wrapper Class object. * </p> * * <p> * NOTE: From v2.2, this method handles {@code Void.TYPE}, returning * {@code Void.TYPE}. * </p> * * @param cls * the class to convert, may be null * @return the wrapper class for {@code cls} or {@code cls} if {@code cls} * is not a primitive. {@code null} if null input. * @since 2.1 */ public static Class<?> primitiveToWrapper(final Class<?> cls) { Class<?> convertedClass = cls; if (cls != null && cls.isPrimitive()) { convertedClass = PRIMITIVE_WRAPPER_MAP.get(cls); } return convertedClass; } /** * <p> * Converts the specified wrapper class to its corresponding primitive * class. * </p> * * <p> * This method is the counter part of {@code primitiveToWrapper()}. If the * passed in class is a wrapper class for a primitive type, this primitive * type will be returned (e.g. {@code Integer.TYPE} for * {@code Integer.class}). For other classes, or if the parameter is * <b>null</b>, the return value is <b>null</b>. * </p> * * @param cls * the class to convert, may be <b>null</b> * @return the corresponding primitive type if {@code cls} is a wrapper * class, <b>null</b> otherwise * @see #primitiveToWrapper(Class) * @since 2.4 */ public static Class<?> wrapperToPrimitive(final Class<?> cls) { return WRAPPER_PRIMITIVE_MAP.get(cls); } /** * <p> * Converts an array of {@code Object} in to an array of {@code Class} * objects. If any of these objects is null, a null element will be inserted * into the array. * </p> * * <p> * This method returns {@code null} for a {@code null} input array. * </p> * * @param array * an {@code Object} array * @return a {@code Class} array, {@code null} if null array input * @since 2.4 */ public static Class<?>[] toClass(final Object... array) { if (array == null) { return null; } else if (array.length == 0) { return ArrayUtils.EMPTY_CLASS_ARRAY; } final Class<?>[] classes = new Class[array.length]; for (int i = 0; i < array.length; i++) { classes[i] = array[i] == null ? null : array[i].getClass(); } return classes; } /* private static final Map<String, Class<?>> PRIMITIVE_MAP = new HashMap<String, Class<?>>(); static { PRIMITIVE_MAP.put("int", int.class); PRIMITIVE_MAP.put("boolean", boolean.class); PRIMITIVE_MAP.put("float", float.class); PRIMITIVE_MAP.put("long", long.class); PRIMITIVE_MAP.put("short", short.class); PRIMITIVE_MAP.put("byte", byte.class); PRIMITIVE_MAP.put("double", double.class); PRIMITIVE_MAP.put("char", char.class); PRIMITIVE_MAP.put("void", void.class); } public static Class<?> forName(String className) throws ClassNotFoundException { if(PRIMITIVE_MAP.containsKey(className)) { return PRIMITIVE_MAP.get(className); } else { return Class.forName(className); } }*/ }