Java tutorial
/* * Copyright (c) 2000, 2013, 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 javax.management.openmbean; // java import // import java.io.InvalidObjectException; import java.io.ObjectStreamException; import java.math.BigDecimal; import java.math.BigInteger; import java.util.Date; import java.util.Map; import java.util.HashMap; // jmx import // import javax.management.ObjectName; /** * The <code>SimpleType</code> class is the <i>open type</i> class whose instances describe * all <i>open data</i> values which are neither arrays, * nor {@link CompositeData CompositeData} values, * nor {@link TabularData TabularData} values. * It predefines all its possible instances as static fields, and has no public constructor. * <p> * Given a <code>SimpleType</code> instance describing values whose Java class name is <i>className</i>, * the internal fields corresponding to the name and description of this <code>SimpleType</code> instance * are also set to <i>className</i>. * In other words, its methods <code>getClassName</code>, <code>getTypeName</code> and <code>getDescription</code> * all return the same string value <i>className</i>. * * @since 1.5 */ public final class SimpleType<T> extends OpenType<T> { /* Serial version */ static final long serialVersionUID = 2215577471957694503L; // SimpleType instances. // IF YOU ADD A SimpleType, YOU MUST UPDATE OpenType and typeArray /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>java.lang.Void</code>. */ public static final SimpleType<Void> VOID = new SimpleType<Void>(Void.class); /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>java.lang.Boolean</code>. */ public static final SimpleType<Boolean> BOOLEAN = new SimpleType<Boolean>(Boolean.class); /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>java.lang.Character</code>. */ public static final SimpleType<Character> CHARACTER = new SimpleType<Character>(Character.class); /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>java.lang.Byte</code>. */ public static final SimpleType<Byte> BYTE = new SimpleType<Byte>(Byte.class); /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>java.lang.Short</code>. */ public static final SimpleType<Short> SHORT = new SimpleType<Short>(Short.class); /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>java.lang.Integer</code>. */ public static final SimpleType<Integer> INTEGER = new SimpleType<Integer>(Integer.class); /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>java.lang.Long</code>. */ public static final SimpleType<Long> LONG = new SimpleType<Long>(Long.class); /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>java.lang.Float</code>. */ public static final SimpleType<Float> FLOAT = new SimpleType<Float>(Float.class); /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>java.lang.Double</code>. */ public static final SimpleType<Double> DOUBLE = new SimpleType<Double>(Double.class); /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>java.lang.String</code>. */ public static final SimpleType<String> STRING = new SimpleType<String>(String.class); /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>java.math.BigDecimal</code>. */ public static final SimpleType<BigDecimal> BIGDECIMAL = new SimpleType<BigDecimal>(BigDecimal.class); /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>java.math.BigInteger</code>. */ public static final SimpleType<BigInteger> BIGINTEGER = new SimpleType<BigInteger>(BigInteger.class); /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>java.util.Date</code>. */ public static final SimpleType<Date> DATE = new SimpleType<Date>(Date.class); /** * The <code>SimpleType</code> instance describing values whose * Java class name is <code>javax.management.ObjectName</code>. */ public static final SimpleType<ObjectName> OBJECTNAME = new SimpleType<ObjectName>(ObjectName.class); private static final SimpleType<?>[] typeArray = { VOID, BOOLEAN, CHARACTER, BYTE, SHORT, INTEGER, LONG, FLOAT, DOUBLE, STRING, BIGDECIMAL, BIGINTEGER, DATE, OBJECTNAME, }; private transient Integer myHashCode = null; // As this instance is immutable, these two values private transient String myToString = null; // need only be calculated once. /* *** Constructor *** */ private SimpleType(Class<T> valueClass) { super(valueClass.getName(), valueClass.getName(), valueClass.getName(), false); } /* *** SimpleType specific information methods *** */ /** * Tests whether <var>obj</var> is a value for this * <code>SimpleType</code> instance. <p> This method returns * <code>true</code> if and only if <var>obj</var> is not null and * <var>obj</var>'s class name is the same as the className field * defined for this <code>SimpleType</code> instance (ie the class * name returned by the {@link OpenType#getClassName() * getClassName} method). * * @param obj the object to be tested. * * @return <code>true</code> if <var>obj</var> is a value for this * <code>SimpleType</code> instance. */ public boolean isValue(Object obj) { // if obj is null, return false // if (obj == null) { return false; } // Test if obj's class name is the same as for this instance // return this.getClassName().equals(obj.getClass().getName()); } /* *** Methods overriden from class Object *** */ /** * Compares the specified <code>obj</code> parameter with this <code>SimpleType</code> instance for equality. * <p> * Two <code>SimpleType</code> instances are equal if and only if their * {@link OpenType#getClassName() getClassName} methods return the same value. * * @param obj the object to be compared for equality with this <code>SimpleType</code> instance; * if <var>obj</var> is <code>null</code> or is not an instance of the class <code>SimpleType</code>, * <code>equals</code> returns <code>false</code>. * * @return <code>true</code> if the specified object is equal to this <code>SimpleType</code> instance. */ public boolean equals(Object obj) { /* If it weren't for readReplace(), we could replace this method with just: return (this == obj); */ if (!(obj instanceof SimpleType<?>)) return false; SimpleType<?> other = (SimpleType<?>) obj; // Test if other's className field is the same as for this instance // return this.getClassName().equals(other.getClassName()); } /** * Returns the hash code value for this <code>SimpleType</code> instance. * The hash code of a <code>SimpleType</code> instance is the hash code of * the string value returned by the {@link OpenType#getClassName() getClassName} method. * <p> * As <code>SimpleType</code> instances are immutable, the hash code for this instance is calculated once, * on the first call to <code>hashCode</code>, and then the same value is returned for subsequent calls. * * @return the hash code value for this <code>SimpleType</code> instance */ public int hashCode() { // Calculate the hash code value if it has not yet been done (ie 1st call to hashCode()) // if (myHashCode == null) { myHashCode = Integer.valueOf(this.getClassName().hashCode()); } // return always the same hash code for this instance (immutable) // return myHashCode.intValue(); } /** * Returns a string representation of this <code>SimpleType</code> instance. * <p> * The string representation consists of * the name of this class (ie <code>javax.management.openmbean.SimpleType</code>) and the type name * for this instance (which is the java class name of the values this <code>SimpleType</code> instance represents). * <p> * As <code>SimpleType</code> instances are immutable, the string representation for this instance is calculated once, * on the first call to <code>toString</code>, and then the same value is returned for subsequent calls. * * @return a string representation of this <code>SimpleType</code> instance */ public String toString() { // Calculate the string representation if it has not yet been done (ie 1st call to toString()) // if (myToString == null) { myToString = this.getClass().getName() + "(name=" + getTypeName() + ")"; } // return always the same string representation for this instance (immutable) // return myToString; } private static final Map<SimpleType<?>, SimpleType<?>> canonicalTypes = new HashMap<SimpleType<?>, SimpleType<?>>(); static { for (int i = 0; i < typeArray.length; i++) { final SimpleType<?> type = typeArray[i]; canonicalTypes.put(type, type); } } /** * Replace an object read from an {@link * java.io.ObjectInputStream} with the unique instance for that * value. * * @return the replacement object. * * @exception ObjectStreamException if the read object cannot be * resolved. */ public Object readResolve() throws ObjectStreamException { final SimpleType<?> canonical = canonicalTypes.get(this); if (canonical == null) { // Should not happen throw new InvalidObjectException("Invalid SimpleType: " + this); } return canonical; } }