Java tutorial
/* * Copyright (c) 2000, 2008, 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.util.Arrays; import javax.management.Descriptor; import javax.management.MBeanConstructorInfo; import javax.management.MBeanParameterInfo; /** * Describes a constructor of an Open MBean. * * * @since 1.5 */ public class OpenMBeanConstructorInfoSupport extends MBeanConstructorInfo implements OpenMBeanConstructorInfo { /* Serial version */ static final long serialVersionUID = -4400441579007477003L; // As this instance is immutable, // these two values need only be calculated once. private transient Integer myHashCode = null; private transient String myToString = null; /** * <p>Constructs an {@code OpenMBeanConstructorInfoSupport} * instance, which describes the constructor of a class of open * MBeans with the specified {@code name}, {@code description} and * {@code signature}.</p> * * <p>The {@code signature} array parameter is internally copied, * so that subsequent changes to the array referenced by {@code * signature} have no effect on this instance.</p> * * @param name cannot be a null or empty string. * * @param description cannot be a null or empty string. * * @param signature can be null or empty if there are no * parameters to describe. * * @throws IllegalArgumentException if {@code name} or {@code * description} are null or empty string. * * @throws ArrayStoreException If {@code signature} is not an * array of instances of a subclass of {@code MBeanParameterInfo}. */ public OpenMBeanConstructorInfoSupport(String name, String description, OpenMBeanParameterInfo[] signature) { this(name, description, signature, (Descriptor) null); } /** * <p>Constructs an {@code OpenMBeanConstructorInfoSupport} * instance, which describes the constructor of a class of open * MBeans with the specified {@code name}, {@code description}, * {@code signature}, and {@code descriptor}.</p> * * <p>The {@code signature} array parameter is internally copied, * so that subsequent changes to the array referenced by {@code * signature} have no effect on this instance.</p> * * @param name cannot be a null or empty string. * * @param description cannot be a null or empty string. * * @param signature can be null or empty if there are no * parameters to describe. * * @param descriptor The descriptor for the constructor. This may * be null which is equivalent to an empty descriptor. * * @throws IllegalArgumentException if {@code name} or {@code * description} are null or empty string. * * @throws ArrayStoreException If {@code signature} is not an * array of instances of a subclass of {@code MBeanParameterInfo}. * * @since 1.6 */ public OpenMBeanConstructorInfoSupport(String name, String description, OpenMBeanParameterInfo[] signature, Descriptor descriptor) { super(name, description, arrayCopyCast(signature), // may throw an ArrayStoreException descriptor); // check parameters that should not be null or empty // (unfortunately it is not done in superclass :-( ! ) // if (name == null || name.trim().isEmpty()) { throw new IllegalArgumentException("Argument name cannot be " + "null or empty"); } if (description == null || description.trim().isEmpty()) { throw new IllegalArgumentException("Argument description cannot " + "be null or empty"); } } private static MBeanParameterInfo[] arrayCopyCast(OpenMBeanParameterInfo[] src) { if (src == null) return null; MBeanParameterInfo[] dst = new MBeanParameterInfo[src.length]; System.arraycopy(src, 0, dst, 0, src.length); // may throw an ArrayStoreException return dst; } /* *** Commodity methods from java.lang.Object *** */ /** * <p>Compares the specified {@code obj} parameter with this * {@code OpenMBeanConstructorInfoSupport} instance for * equality.</p> * * <p>Returns {@code true} if and only if all of the following * statements are true: * * <ul> * <li>{@code obj} is non null,</li> * <li>{@code obj} also implements the {@code * OpenMBeanConstructorInfo} interface,</li> * <li>their names are equal</li> * <li>their signatures are equal.</li> * </ul> * * This ensures that this {@code equals} method works properly for * {@code obj} parameters which are different implementations of * the {@code OpenMBeanConstructorInfo} interface. * * @param obj the object to be compared for equality with this * {@code OpenMBeanConstructorInfoSupport} instance; * * @return {@code true} if the specified object is equal to this * {@code OpenMBeanConstructorInfoSupport} instance. */ public boolean equals(Object obj) { // if obj is null, return false // if (obj == null) { return false; } // if obj is not a OpenMBeanConstructorInfo, return false // OpenMBeanConstructorInfo other; try { other = (OpenMBeanConstructorInfo) obj; } catch (ClassCastException e) { return false; } // Now, really test for equality between this // OpenMBeanConstructorInfo implementation and the other: // // their Name should be equal if (!this.getName().equals(other.getName())) { return false; } // their Signatures should be equal if (!Arrays.equals(this.getSignature(), other.getSignature())) { return false; } // All tests for equality were successfull // return true; } /** * <p>Returns the hash code value for this {@code * OpenMBeanConstructorInfoSupport} instance.</p> * * <p>The hash code of an {@code OpenMBeanConstructorInfoSupport} * instance is the sum of the hash codes of all elements of * information used in {@code equals} comparisons (ie: its name * and signature, where the signature hashCode is calculated by a * call to {@code * java.util.Arrays.asList(this.getSignature).hashCode()}).</p> * * <p>This ensures that {@code t1.equals(t2)} implies that {@code * t1.hashCode()==t2.hashCode()} for any two {@code * OpenMBeanConstructorInfoSupport} instances {@code t1} and * {@code t2}, as required by the general contract of the method * {@link Object#hashCode() Object.hashCode()}.</p> * * <p>However, note that another instance of a class implementing * the {@code OpenMBeanConstructorInfo} interface may be equal to * this {@code OpenMBeanConstructorInfoSupport} instance as * defined by {@link #equals(java.lang.Object)}, but may have a * different hash code if it is calculated differently.</p> * * <p>As {@code OpenMBeanConstructorInfoSupport} 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.</p> * * @return the hash code value for this {@code * OpenMBeanConstructorInfoSupport} instance */ public int hashCode() { // Calculate the hash code value if it has not yet been done // (ie 1st call to hashCode()) // if (myHashCode == null) { int value = 0; value += this.getName().hashCode(); value += Arrays.asList(this.getSignature()).hashCode(); myHashCode = Integer.valueOf(value); } // return always the same hash code for this instance (immutable) // return myHashCode.intValue(); } /** * <p>Returns a string representation of this {@code * OpenMBeanConstructorInfoSupport} instance.</p> * * <p>The string representation consists of the name of this class * (ie {@code * javax.management.openmbean.OpenMBeanConstructorInfoSupport}), * the name and signature of the described constructor and the * string representation of its descriptor.</p> * * <p>As {@code OpenMBeanConstructorInfoSupport} 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.</p> * * @return a string representation of this {@code * OpenMBeanConstructorInfoSupport} instance */ public String toString() { // Calculate the string value if it has not yet been done (ie // 1st call to toString()) // if (myToString == null) { myToString = new StringBuilder().append(this.getClass().getName()).append("(name=") .append(this.getName()).append(",signature=") .append(Arrays.asList(this.getSignature()).toString()).append(",descriptor=") .append(this.getDescriptor()).append(")").toString(); } // return always the same string representation for this // instance (immutable) // return myToString; } }