Java tutorial
/* * Copyright (c) 2000, 2017, 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. */ /* * @author IBM Corp. * * Copyright IBM Corp. 1999-2000. All rights reserved. */ package javax.management; import java.io.Serializable; // Javadoc imports: import java.lang.management.MemoryUsage; import java.util.Arrays; import java.util.Locale; import java.util.ResourceBundle; import javax.management.openmbean.CompositeData; import javax.management.openmbean.OpenMBeanAttributeInfoSupport; import javax.management.openmbean.OpenMBeanOperationInfoSupport; import javax.management.openmbean.OpenMBeanParameterInfoSupport; import javax.management.openmbean.OpenType; /** * <p>Additional metadata for a JMX element. A {@code Descriptor} * is associated with a {@link MBeanInfo}, {@link MBeanAttributeInfo}, etc. * It consists of a collection of fields. A field is a name and an * associated value.</p> * * <p>Field names are not case-sensitive. The names {@code descriptorType}, * {@code descriptortype}, and {@code DESCRIPTORTYPE} are all equivalent. * However, the case that was used when the field was first set is preserved * in the result of the {@link #getFields} and {@link #getFieldNames} * methods.</p> * * <p>Not all field names and values are predefined. * New fields can be defined and added by any program.</p> * * <p>A descriptor can be mutable or immutable. * An immutable descriptor, once created, never changes. * The <code>Descriptor</code> methods that could modify the contents * of the descriptor will throw an exception * for an immutable descriptor. Immutable descriptors are usually * instances of {@link ImmutableDescriptor} or a subclass. Mutable * descriptors are usually instances of * {@link javax.management.modelmbean.DescriptorSupport} or a subclass. * * <p>Certain fields are used by the JMX implementation. This means * either that the presence of the field may change the behavior of * the JMX API or that the field may be set in descriptors returned by * the JMX API. These fields appear in <i>italics</i> in the table * below, and each one has a corresponding constant in the {@link JMX} * class. For example, the field {@code defaultValue} is represented * by the constant {@link JMX#DEFAULT_VALUE_FIELD}.</p> * * <p>Certain other fields have conventional meanings described in the * table below but they are not required to be understood or set by * the JMX implementation.</p> * * <p>Field names defined by the JMX specification in this and all * future versions will never contain a period (.). Users can safely * create their own fields by including a period in the name and be * sure that these names will not collide with any future version of * the JMX API. It is recommended to follow the Java package naming * convention to avoid collisions between field names from different * origins. For example, a field created by {@code example.com} might * have the name {@code com.example.interestLevel}.</p> * * <p>Note that the values in the {@code defaultValue}, {@code * legalValues}, {@code maxValue}, and {@code minValue} fields should * be consistent with the type returned by the {@code getType()} * method for the associated {@code MBeanAttributeInfo} or {@code * MBeanParameterInfo}. For MXBeans, this means that they should be * of the mapped Java type, called <em>opendata</em>(J) in the <a * href="MXBean.html#mapping-rules">MXBean type mapping rules</a>.</p> * * <table class="striped"> * <caption style="display:none">Descriptor Fields</caption> * <thead> * <tr><th scope="col">Name</th> * <th scope="col">Type</th> * <th scope="col">Used in</th> * <th scope="col">Meaning</th></tr> * </thead> * * <tbody style="text-align:left"> * <tr id="defaultValue"><th scope="row"><i>defaultValue</i><td>Object</td> * <td>MBeanAttributeInfo<br>MBeanParameterInfo</td> * * <td>Default value for an attribute or parameter. See * {@link javax.management.openmbean}.</td> * * <tr><th scope="row">deprecated</th><td>String</td><td>Any</td> * * <td>An indication that this element of the information model is no * longer recommended for use. A set of MBeans defined by an * application is collectively called an <em>information model</em>. * The convention is for the value of this field to contain a string * that is the version of the model in which the element was first * deprecated, followed by a space, followed by an explanation of the * deprecation, for example {@code "1.3 Replaced by the Capacity * attribute"}.</td> * * <tr><th scope="row" id="descriptionResourceBundleBaseName">descriptionResource<br> * BundleBaseName</th><td>String</td><td>Any</td> * * <td>The base name for the {@link ResourceBundle} in which the key given in * the {@code descriptionResourceKey} field can be found, for example * {@code "com.example.myapp.MBeanResources"}. The meaning of this * field is defined by this specification but the field is not set or * used by the JMX API itself.</td> * * <tr><th scope="row" id="descriptionResourceKey">descriptionResourceKey</th> * <td>String</td><td>Any</td> * * <td>A resource key for the description of this element. In * conjunction with the {@code descriptionResourceBundleBaseName}, * this can be used to find a localized version of the description. * The meaning of this field is defined by this specification but the * field is not set or used by the JMX API itself.</td> * * <tr><th scope="row">enabled</th><td>String</td> * <td>MBeanAttributeInfo<br>MBeanNotificationInfo<br>MBeanOperationInfo</td> * * <td>The string {@code "true"} or {@code "false"} according as this * item is enabled. When an attribute or operation is not enabled, it * exists but cannot currently be accessed. A user interface might * present it as a greyed-out item. For example, an attribute might * only be meaningful after the {@code start()} method of an MBean has * been called, and is otherwise disabled. Likewise, a notification * might be disabled if it cannot currently be emitted but could be in * other circumstances.</td> * * <tr id="exceptions"><th scope="row">exceptions<td>String[]</td> * <td>MBeanAttributeInfo, MBeanConstructorInfo, MBeanOperationInfo</td> * * <td>The class names of the exceptions that can be thrown when invoking a * constructor or operation, or getting an attribute. The meaning of this field * is defined by this specification but the field is not set or used by the * JMX API itself. Exceptions thrown when * setting an attribute are specified by the field * <a href="#setExceptions">{@code setExceptions}</a>. * * <tr id="immutableInfo"><th scope="row"><i>immutableInfo</i><td>String</td> * <td>MBeanInfo</td> * * <td>The string {@code "true"} or {@code "false"} according as this * MBean's MBeanInfo is <em>immutable</em>. When this field is true, * the MBeanInfo for the given MBean is guaranteed not to change over * the lifetime of the MBean. Hence, a client can read it once and * cache the read value. When this field is false or absent, there is * no such guarantee, although that does not mean that the MBeanInfo * will necessarily change. See also the <a * href="MBeanInfo.html#info-changed">{@code "jmx.mbean.info.changed"}</a> * notification.</td> * * <tr id="infoTimeout"><th scope="row">infoTimeout</th><td>String<br>Long</td><td>MBeanInfo</td> * * <td>The time in milli-seconds that the MBeanInfo can reasonably be * expected to be unchanged. The value can be a {@code Long} or a * decimal string. This provides a hint from a DynamicMBean or any * MBean that does not define {@code immutableInfo} as {@code true} * that the MBeanInfo is not likely to change within this period and * therefore can be cached. When this field is missing or has the * value zero, it is not recommended to cache the MBeanInfo unless it * has the {@code immutableInfo} set to {@code true} or it has <a * href="MBeanInfo.html#info-changed">{@code "jmx.mbean.info.changed"}</a> in * its {@link MBeanNotificationInfo} array.</td></tr> * * <tr id="interfaceClassName"><th scope="row"><i>interfaceClassName</i></th> * <td>String</td><td>MBeanInfo</td> * * <td>The Java interface name for a Standard MBean or MXBean, as * returned by {@link Class#getName()}. A Standard MBean or MXBean * registered directly in the MBean Server or created using the {@link * StandardMBean} class will have this field in its MBeanInfo * Descriptor.</td> * * <tr id="legalValues"><th scope="row"><i>legalValues</i></th> * <td>{@literal Set<?>}</td><td>MBeanAttributeInfo<br>MBeanParameterInfo</td> * * <td>Legal values for an attribute or parameter. See * {@link javax.management.openmbean}.</td> * * <tr id="locale"><th scope="row">locale</th> * <td>String</td><td>Any</td> * * <td>The {@linkplain Locale locale} of the description in this * {@code MBeanInfo}, {@code MBeanAttributeInfo}, etc, as returned * by {@link Locale#toString()}.</td> * * <tr id="maxValue"><th scope="row"><i>maxValue</i><td>Object</td> * <td>MBeanAttributeInfo<br>MBeanParameterInfo</td> * * <td>Maximum legal value for an attribute or parameter. See * {@link javax.management.openmbean}.</td> * * <tr id="metricType"><th scope="row">metricType</th><td>String</td> * <td>MBeanAttributeInfo<br>MBeanOperationInfo</td> * * <td>The type of a metric, one of the strings "counter" or "gauge". * A metric is a measurement exported by an MBean, usually an * attribute but sometimes the result of an operation. A metric that * is a <em>counter</em> has a value that never decreases except by * being reset to a starting value. Counter metrics are almost always * non-negative integers. An example might be the number of requests * received. A metric that is a <em>gauge</em> has a numeric value * that can increase or decrease. Examples might be the number of * open connections or a cache hit rate or a temperature reading. * * <tr id="minValue"><th scope="row"><i>minValue</i><td>Object</td> * <td>MBeanAttributeInfo<br>MBeanParameterInfo</td> * * <td>Minimum legal value for an attribute or parameter. See * {@link javax.management.openmbean}.</td> * * <tr id="mxbean"><th scope="row"><i>mxbean</i><td>String</td> * <td>MBeanInfo</td> * * <td>The string {@code "true"} or {@code "false"} according as this * MBean is an {@link MXBean}. A Standard MBean or MXBean registered * directly with the MBean Server or created using the {@link * StandardMBean} class will have this field in its MBeanInfo * Descriptor.</td> * * <tr id="openType"><th scope="row"><i>openType</i><td>{@link OpenType}</td> * <td>MBeanAttributeInfo<br>MBeanOperationInfo<br>MBeanParameterInfo</td> * * <td><p>The Open Type of this element. In the case of {@code * MBeanAttributeInfo} and {@code MBeanParameterInfo}, this is the * Open Type of the attribute or parameter. In the case of {@code * MBeanOperationInfo}, it is the Open Type of the return value. This * field is set in the Descriptor for all instances of {@link * OpenMBeanAttributeInfoSupport}, {@link * OpenMBeanOperationInfoSupport}, and {@link * OpenMBeanParameterInfoSupport}. It is also set for attributes, * operations, and parameters of MXBeans.</p> * * <p>This field can be set for an {@code MBeanNotificationInfo}, in * which case it indicates the Open Type that the {@link * Notification#getUserData() user data} will have.</td> * * <tr id="originalType"><th scope="row"><i>originalType</i><td>String</td> * <td>MBeanAttributeInfo<br>MBeanOperationInfo<br>MBeanParameterInfo</td> * * <td><p>The original Java type of this element as it appeared in the * {@link MXBean} interface method that produced this {@code * MBeanAttributeInfo} (etc). For example, a method<br> <code>public * </code> {@link MemoryUsage}<code> getHeapMemoryUsage();</code><br> * in an MXBean interface defines an attribute called {@code * HeapMemoryUsage} of type {@link CompositeData}. The {@code * originalType} field in the Descriptor for this attribute will have * the value {@code "java.lang.management.MemoryUsage"}. * * <p>The format of this string is described in the section <a * href="MXBean.html#type-names">Type Names</a> of the MXBean * specification.</p> * * <tr id="setExceptions"><th scope="row"><i>setExceptions</i><td>String[]</td> * <td>MBeanAttributeInfo</td> * * <td>The class names of the exceptions that can be thrown when setting * an attribute. The meaning of this field * is defined by this specification but the field is not set or used by the * JMX API itself. Exceptions thrown when getting an attribute are specified * by the field <a href="#exceptions">{@code exceptions}</a>. * * <tr><th scope="row">severity</th><td>String<br>Integer</td> * <td>MBeanNotificationInfo</td> * * <td>The severity of this notification. It can be 0 to mean * unknown severity or a value from 1 to 6 representing decreasing * levels of severity. It can be represented as a decimal string or * an {@code Integer}.</td> * * <tr><th scope="row">since</th><td>String</td><td>Any</td> * * <td>The version of the information model in which this element * was introduced. A set of MBeans defined by an application is * collectively called an <em>information model</em>. The * application may also define versions of this model, and use the * {@code "since"} field to record the version in which an element * first appeared.</td> * * <tr><th scope="row">units</th><td>String</td> * <td>MBeanAttributeInfo<br>MBeanParameterInfo<br>MBeanOperationInfo</td> * * <td>The units in which an attribute, parameter, or operation return * value is measured, for example {@code "bytes"} or {@code * "seconds"}.</td> * * </tbody> * </table> * * <p>Some additional fields are defined by Model MBeans. See the * information for <a href="modelmbean/ModelMBeanInfo.html#descriptor"><!-- * -->{@code ModelMBeanInfo}</a>, * <a href="modelmbean/ModelMBeanAttributeInfo.html#descriptor"><!-- * -->{@code ModelMBeanAttributeInfo}</a>, * <a href="modelmbean/ModelMBeanConstructorInfo.html#descriptor"><!-- * -->{@code ModelMBeanConstructorInfo}</a>, * <a href="modelmbean/ModelMBeanNotificationInfo.html#descriptor"><!-- * -->{@code ModelMBeanNotificationInfo}</a>, and * <a href="modelmbean/ModelMBeanOperationInfo.html#descriptor"><!-- * -->{@code ModelMBeanOperationInfo}</a>, as * well as the chapter "Model MBeans" of the <a * href="http://www.oracle.com/technetwork/java/javase/tech/javamanagement-140525.html">JMX * Specification</a>. The following table summarizes these fields. Note * that when the Type in this table is Number, a String that is the decimal * representation of a Long can also be used.</p> * * <p>Nothing prevents the use of these fields in MBeans that are not Model * MBeans. The <a href="#displayName">displayName</a>, <a href="#severity"><!-- * -->severity</a>, and <a href="#visibility">visibility</a> fields are of * interest outside Model MBeans, for example. But only Model MBeans have * a predefined behavior for these fields.</p> * * <table class="striped"> * <caption style="display:none">ModelMBean Fields</caption> * * <thead> * <tr><th scope="col">Name</th> * <th scope="col">Type</th> * <th scope="col">Used in</th> * <th scope="col">Meaning</th></tr> * </thead> * * <tbody style="text-align:left"> * <tr><th scope="row">class</th><td>String</td><td>ModelMBeanOperationInfo</td> * <td>Class where method is defined (fully qualified).</td></tr> * * <tr><th scope="row">currencyTimeLimit</th><td>Number</td> * <td>ModelMBeanInfo<br>ModelMBeanAttributeInfo<br>ModelMBeanOperationInfo</td> * <td>How long cached value is valid: <0 never, =0 always, * >0 seconds.</td></tr> * * <tr><th scope="row">default</th><td>Object</td><td>ModelMBeanAttributeInfo</td> * <td>Default value for attribute.</td></tr> * * <tr><th scope="row">descriptorType</th><td>String</td><td>Any</td> * <td>Type of descriptor, "mbean", "attribute", "constructor", "operation", * or "notification".</td></tr> * * <tr id="displayName"><th scope="row">displayName</th><td>String</td><td>Any</td> * <td>Human readable name of this item.</td></tr> * * <tr><th scope="row">export</th><td>String</td><td>ModelMBeanInfo</td> * <td>Name to be used to export/expose this MBean so that it is * findable by other JMX Agents.</td></tr> * * <tr><th scope="row">getMethod</th><td>String</td><td>ModelMBeanAttributeInfo</td> * <td>Name of operation descriptor for get method.</td></tr> * * <tr><th scope="row">lastUpdatedTimeStamp</th><td>Number</td> * <td>ModelMBeanAttributeInfo<br>ModelMBeanOperationInfo</td> * <td>When <a href="#value-field">value</a> was set.</td></tr> * * <tr><th scope="row">log</th><td>String</td><td>ModelMBeanInfo<br>ModelMBeanNotificationInfo</td> * <td>t or T: log all notifications, f or F: log no notifications.</td></tr> * * <tr><th scope="row">logFile</th><td>String</td><td>ModelMBeanInfo<br>ModelMBeanNotificationInfo</td> * <td>Fully qualified filename to log events to.</td></tr> * * <tr><th scope="row">messageID</th><td>String</td><td>ModelMBeanNotificationInfo</td> * <td>Unique key for message text (to allow translation, analysis).</td></tr> * * <tr><th scope="row">messageText</th><td>String</td><td>ModelMBeanNotificationInfo</td> * <td>Text of notification.</td></tr> * * <tr><th scope="row">name</th><td>String</td><td>Any</td> * <td>Name of this item.</td></tr> * * <tr><th scope="row">persistFile</th><td>String</td><td>ModelMBeanInfo</td> * <td>File name into which the MBean should be persisted.</td></tr> * * <tr><th scope="row">persistLocation</th><td>String</td><td>ModelMBeanInfo</td> * <td>The fully qualified directory name where the MBean should be * persisted (if appropriate).</td></tr> * * <tr><th scope="row">persistPeriod</th><td>Number</td> * <td>ModelMBeanInfo<br>ModelMBeanAttributeInfo</td> * <td>Frequency of persist cycle in seconds. Used when persistPolicy is * "OnTimer" or "NoMoreOftenThan".</td></tr> * * <tr><th scope="row">persistPolicy</th><td>String</td> * <td>ModelMBeanInfo<br>ModelMBeanAttributeInfo</td> * <td>One of: OnUpdate|OnTimer|NoMoreOftenThan|OnUnregister|Always|Never. * See the section "MBean Descriptor Fields" in the JMX specification * document.</td></tr> * * <tr><th scope="row">presentationString</th><td>String</td><td>Any</td> * <td>XML formatted string to allow presentation of data.</td></tr> * * <tr><th scope="row">protocolMap</th><td>Descriptor</td><td>ModelMBeanAttributeInfo</td> * <td>See the section "Protocol Map Support" in the JMX specification * document. Mappings must be appropriate for the attribute and entries * can be updated or augmented at runtime.</td></tr> * * <tr><th scope="row">role</th><td>String</td> * <td>ModelMBeanConstructorInfo<br>ModelMBeanOperationInfo</td> * <td>One of "constructor", "operation", "getter", or "setter".</td></tr> * * <tr><th scope="row">setMethod</th><td>String</td><td>ModelMBeanAttributeInfo</td> * <td>Name of operation descriptor for set method.</td></tr> * * <tr id="severity"><th scope="row">severity</th><td>Number</td> * <td>ModelMBeanNotificationInfo</td> * <td>0-6 where 0: unknown; 1: non-recoverable; * 2: critical, failure; 3: major, severe; * 4: minor, marginal, error; 5: warning; * 6: normal, cleared, informative</td></tr> * * <tr><th scope="row">targetObject</th><td>Object</td><td>ModelMBeanOperationInfo</td> * <td>Object on which to execute this method.</td></tr> * * <tr><th scope="row">targetType</th><td>String</td><td>ModelMBeanOperationInfo</td> * <td>type of object reference for targetObject. Can be: * ObjectReference | Handle | EJBHandle | IOR | RMIReference.</td></tr> * * <tr id="value-field"><th scope="row">value</th><td>Object</td> * <td>ModelMBeanAttributeInfo<br>ModelMBeanOperationInfo</td> * <td>Current (cached) value for attribute or operation.</td></tr> * * <tr id="visibility"><th scope="row">visibility</th><td>Number</td><td>Any</td> * <td>1-4 where 1: always visible, 4: rarely visible.</td></tr> * * </tbody> * </table> * * @since 1.5 */ public interface Descriptor extends Serializable, Cloneable { /** * Returns the value for a specific field name, or null if no value * is present for that name. * * @param fieldName the field name. * * @return the corresponding value, or null if the field is not present. * * @exception RuntimeOperationsException if the field name is illegal. */ public Object getFieldValue(String fieldName) throws RuntimeOperationsException; /** * <p>Sets the value for a specific field name. This will * modify an existing field or add a new field.</p> * * <p>The field value will be validated before it is set. * If it is not valid, then an exception will be thrown. * The meaning of validity is dependent on the descriptor * implementation.</p> * * @param fieldName The field name to be set. Cannot be null or empty. * @param fieldValue The field value to be set for the field * name. Can be null if that is a valid value for the field. * * @exception RuntimeOperationsException if the field name or field value * is illegal (wrapped exception is {@link IllegalArgumentException}); or * if the descriptor is immutable (wrapped exception is * {@link UnsupportedOperationException}). */ public void setField(String fieldName, Object fieldValue) throws RuntimeOperationsException; /** * Returns all of the fields contained in this descriptor as a string array. * * @return String array of fields in the format <i>fieldName=fieldValue</i> * <br>If the value of a field is not a String, then the toString() method * will be called on it and the returned value, enclosed in parentheses, * used as the value for the field in the returned array. If the value * of a field is null, then the value of the field in the returned array * will be empty. If the descriptor is empty, you will get * an empty array. * * @see #setFields */ public String[] getFields(); /** * Returns all the field names in the descriptor. * * @return String array of field names. If the descriptor is empty, * you will get an empty array. */ public String[] getFieldNames(); /** * Returns all the field values in the descriptor as an array of Objects. The * returned values are in the same order as the {@code fieldNames} String array parameter. * * @param fieldNames String array of the names of the fields that * the values should be returned for. If the array is empty then * an empty array will be returned. If the array is null then all * values will be returned, as if the parameter were the array * returned by {@link #getFieldNames()}. If a field name in the * array does not exist, including the case where it is null or * the empty string, then null is returned for the matching array * element being returned. * * @return Object array of field values. If the list of {@code fieldNames} * is empty, you will get an empty array. */ public Object[] getFieldValues(String... fieldNames); /** * Removes a field from the descriptor. * * @param fieldName String name of the field to be removed. * If the field name is illegal or the field is not found, * no exception is thrown. * * @exception RuntimeOperationsException if a field of the given name * exists and the descriptor is immutable. The wrapped exception will * be an {@link UnsupportedOperationException}. */ public void removeField(String fieldName); /** * <p>Sets all fields in the field names array to the new value with * the same index in the field values array. Array sizes must match.</p> * * <p>The field value will be validated before it is set. * If it is not valid, then an exception will be thrown. * If the arrays are empty, then no change will take effect.</p> * * @param fieldNames String array of field names. The array and array * elements cannot be null. * @param fieldValues Object array of the corresponding field values. * The array cannot be null. Elements of the array can be null. * * @throws RuntimeOperationsException if the change fails for any reason. * Wrapped exception is {@link IllegalArgumentException} if * {@code fieldNames} or {@code fieldValues} is null, or if * the arrays are of different lengths, or if there is an * illegal value in one of them. * Wrapped exception is {@link UnsupportedOperationException} * if the descriptor is immutable, and the call would change * its contents. * * @see #getFields */ public void setFields(String[] fieldNames, Object[] fieldValues) throws RuntimeOperationsException; /** * <p>Returns a descriptor which is equal to this descriptor. * Changes to the returned descriptor will have no effect on this * descriptor, and vice versa. If this descriptor is immutable, * it may fulfill this condition by returning itself.</p> * @exception RuntimeOperationsException for illegal value for field names * or field values. * If the descriptor construction fails for any reason, this exception will * be thrown. * @return A descriptor which is equal to this descriptor. */ public Object clone() throws RuntimeOperationsException; /** * Returns true if all of the fields have legal values given their * names. * * @return true if the values are legal. * * @exception RuntimeOperationsException If the validity checking fails for * any reason, this exception will be thrown. * The method returns false if the descriptor is not valid, but throws * this exception if the attempt to determine validity fails. */ public boolean isValid() throws RuntimeOperationsException; /** * <p>Compares this descriptor to the given object. The objects are equal if * the given object is also a Descriptor, and if the two Descriptors have * the same field names (possibly differing in case) and the same * associated values. The respective values for a field in the two * Descriptors are equal if the following conditions hold:</p> * * <ul> * <li>If one value is null then the other must be too.</li> * <li>If one value is a primitive array then the other must be a primitive * array of the same type with the same elements.</li> * <li>If one value is an object array then the other must be too and * {@link Arrays#deepEquals(Object[],Object[])} must return true.</li> * <li>Otherwise {@link Object#equals(Object)} must return true.</li> * </ul> * * @param obj the object to compare with. * * @return {@code true} if the objects are the same; {@code false} * otherwise. * * @since 1.6 */ public boolean equals(Object obj); /** * <p>Returns the hash code value for this descriptor. The hash * code is computed as the sum of the hash codes for each field in * the descriptor. The hash code of a field with name {@code n} * and value {@code v} is {@code n.toLowerCase().hashCode() ^ h}. * Here {@code h} is the hash code of {@code v}, computed as * follows:</p> * * <ul> * <li>If {@code v} is null then {@code h} is 0.</li> * <li>If {@code v} is a primitive array then {@code h} is computed using * the appropriate overloading of {@code java.util.Arrays.hashCode}.</li> * <li>If {@code v} is an object array then {@code h} is computed using * {@link Arrays#deepHashCode(Object[])}.</li> * <li>Otherwise {@code h} is {@code v.hashCode()}.</li> * </ul> * * @return A hash code value for this object. * * @since 1.6 */ public int hashCode(); }