Java example source code file (SimpleType.java)

This example Java source code file (SimpleType.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

bigdecimal, biginteger, boolean, byte, date, double, float, integer, long, management, math, objectname, short, simpletype, string, util, void

The SimpleType.java Java example source code

/*
 * 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 class is the open type class whose instances describe
 * all <i>open data 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 instance describing values whose Java class name is className,
 * the internal fields corresponding to the name and description of this <code>SimpleType instance
 * are also set to <i>className.
 * In other words, its methods <code>getClassName, getTypeName and getDescription
 * all return the same string value <i>className.
 *
 * @since 1.5
 */
public final class SimpleType<T> extends OpenType {

    /* Serial version */
    static final long serialVersionUID = 2215577471957694503L;

    // SimpleType instances.
    // IF YOU ADD A SimpleType, YOU MUST UPDATE OpenType and typeArray

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>java.lang.Void.
     */
    public static final SimpleType<Void> VOID =
        new SimpleType<Void>(Void.class);

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>java.lang.Boolean.
     */
    public static final SimpleType<Boolean> BOOLEAN =
        new SimpleType<Boolean>(Boolean.class);

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>java.lang.Character.
     */
    public static final SimpleType<Character> CHARACTER =
        new SimpleType<Character>(Character.class);

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>java.lang.Byte.
     */
    public static final SimpleType<Byte> BYTE =
        new SimpleType<Byte>(Byte.class);

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>java.lang.Short.
     */
    public static final SimpleType<Short> SHORT =
        new SimpleType<Short>(Short.class);

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>java.lang.Integer.
     */
    public static final SimpleType<Integer> INTEGER =
        new SimpleType<Integer>(Integer.class);

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>java.lang.Long.
     */
    public static final SimpleType<Long> LONG =
        new SimpleType<Long>(Long.class);

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>java.lang.Float.
     */
    public static final SimpleType<Float> FLOAT =
        new SimpleType<Float>(Float.class);

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>java.lang.Double.
     */
    public static final SimpleType<Double> DOUBLE =
        new SimpleType<Double>(Double.class);

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>java.lang.String.
     */
    public static final SimpleType<String> STRING =
        new SimpleType<String>(String.class);

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>java.math.BigDecimal.
     */
    public static final SimpleType<BigDecimal> BIGDECIMAL =
        new SimpleType<BigDecimal>(BigDecimal.class);

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>java.math.BigInteger.
     */
    public static final SimpleType<BigInteger> BIGINTEGER =
        new SimpleType<BigInteger>(BigInteger.class);

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>java.util.Date.
     */
    public static final SimpleType<Date> DATE =
        new SimpleType<Date>(Date.class);

    /**
     * The <code>SimpleType instance describing values whose
     * Java class name is <code>javax.management.ObjectName.
     */
    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 is a value for this
     * <code>SimpleType instance.  
 This method returns
     * <code>true if and only if obj is not null and
     * <var>obj's class name is the same as the className field
     * defined for this <code>SimpleType instance (ie the class
     * name returned by the {@link OpenType#getClassName()
     * getClassName} method).
     *
     * @param obj the object to be tested.
     *
     * @return <code>true if obj is a value for this
     * <code>SimpleType 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 parameter with this SimpleType instance for equality.
     * <p>
     * Two <code>SimpleType 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 instance;
     *              if <var>obj is null or is not an instance of the class SimpleType,
     *              <code>equals returns false.
     *
     * @return  <code>true if the specified object is equal to this SimpleType 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 instance.
     * The hash code of a <code>SimpleType instance is the the hash code of
     * the string value returned by the {@link OpenType#getClassName() getClassName} method.
     * <p>
     * As <code>SimpleType instances are immutable, the hash code for this instance is calculated once,
     * on the first call to <code>hashCode, and then the same value is returned for subsequent calls.
     *
     * @return  the hash code value for this <code>SimpleType 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 instance.
     * <p>
     * The string representation consists of
     * the name of this class (ie <code>javax.management.openmbean.SimpleType) and the type name
     * for this instance (which is the java class name of the values this <code>SimpleType instance represents).
     * <p>
     * As <code>SimpleType instances are immutable, the string representation for this instance is calculated once,
     * on the first call to <code>toString, and then the same value is returned for subsequent calls.
     *
     * @return  a string representation of this <code>SimpleType 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> canonicalTypes =
        new HashMap<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;
    }
}