HashCode 使用产生Utils类

本文主要是介绍HashCode 使用产生Utils类，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

hashCode 和equals 这两个方法一直是使用的焦点！我们在使用比较对象的使用很多情况下都要使用这个，随便使用将造成很多困扰，详情见-effectjava

无意中发现一个写的还不错的utils 类，专门为了这个二创造的。
以17为底数，37为乘

package org.apache.commons.httpclient.util;public class LangUtils {public static final int HASH_SEED = 17;public static final int HASH_OFFSET = 37;private LangUtils() {super();}public static int hashCode(final int seed, final int hashcode) {return seed * HASH_OFFSET + hashcode;}public static int hashCode(final int seed, final Object obj) {return hashCode(seed, obj != null ? obj.hashCode() : 0);}public static int hashCode(final int seed, final boolean b) {return hashCode(seed, b ? 1 : 0);}public static boolean equals(final Object obj1, final Object obj2) {return obj1 == null ? obj2 == null : obj1.equals(obj2);}}

httpPost这个类很好的说明在使用equlas 和 hashcode

/** $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//httpclient/src/java/org/apache/commons/httpclient/HttpHost.java,v 1.3 2005/01/14 21:16:40 olegk Exp $* $Revision: 510587 $* $Date: 2007-02-22 17:56:08 +0100 (Thu, 22 Feb 2007) $** ====================================================================**  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.* ====================================================================** This software consists of voluntary contributions made by many* individuals on behalf of the Apache Software Foundation.  For more* information on the Apache Software Foundation, please see* <http://www.apache.org/>.**/package org.apache.commons.httpclient;import org.apache.commons.httpclient.protocol.Protocol;
import org.apache.commons.httpclient.util.LangUtils;/*** Holds all of the variables needed to describe an HTTP connection to a host. This includes * remote host, port and protocol.* * @author <a href="mailto:becke@u.washington.edu">Michael Becke</a>* @author <a href="mailto:mbowler@GargoyleSoftware.com">Mike Bowler</a>* @author <a href="mailto:oleg@ural.ru">Oleg Kalnichevski</a>* @author Laura Werner* * @since 3.0 */
public class HttpHost implements Cloneable {/** The host to use. */private String hostname = null;/** The port to use. */private int port = -1;/** The protocol */private Protocol protocol = null;/*** Constructor for HttpHost.*   * @param hostname the hostname (IP or DNS name). Can be <code>null</code>.* @param port the port. Value <code>-1</code> can be used to set default protocol port* @param protocol the protocol. Value <code>null</code> can be used to set default protocol*/public HttpHost(final String hostname, int port, final Protocol protocol) {super();if (hostname == null) {throw new IllegalArgumentException("Host name may not be null");}if (protocol == null) {throw new IllegalArgumentException("Protocol may not be null");}this.hostname = hostname;this.protocol = protocol;if (port >= 0) {this.port = port;} else {this.port = this.protocol.getDefaultPort();}}/*** Constructor for HttpHost.*   * @param hostname the hostname (IP or DNS name). Can be <code>null</code>.* @param port the port. Value <code>-1</code> can be used to set default protocol port*/public HttpHost(final String hostname, int port) {this(hostname, port, Protocol.getProtocol("http"));}/*** Constructor for HttpHost.*   * @param hostname the hostname (IP or DNS name). Can be <code>null</code>.*/public HttpHost(final String hostname) {this(hostname, -1, Protocol.getProtocol("http"));}/*** URI constructor for HttpHost.*   * @param uri the URI.*/public  HttpHost(final URI uri) throws URIException {this(uri.getHost(), uri.getPort(), Protocol.getProtocol(uri.getScheme()));}/*** Copy constructor for HttpHost* * @param httphost the HTTP host to copy details from*/public HttpHost (final HttpHost httphost) {super();init(httphost);}private void init(final HttpHost httphost) {this.hostname = httphost.hostname;this.port = httphost.port;this.protocol = httphost.protocol;}/*** @throws CloneNotSupportedException * @see java.lang.Object#clone()*/public Object clone() throws CloneNotSupportedException {HttpHost copy = (HttpHost) super.clone();copy.init(this);return copy;}    /*** Returns the host name (IP or DNS name).* * @return the host name (IP or DNS name), or <code>null</code> if not set*/public String getHostName() {return this.hostname;}/*** Returns the port.* * @return the host port, or <code>-1</code> if not set*/public int getPort() {return this.port;}/*** Returns the protocol.* @return The protocol.*/public Protocol getProtocol() {return this.protocol;}/*** Return the host uri.* * @return The host uri.*/public String toURI() {StringBuffer buffer = new StringBuffer(50);        buffer.append(this.protocol.getScheme());buffer.append("://");buffer.append(this.hostname);if (this.port != this.protocol.getDefaultPort()) {buffer.append(':');buffer.append(this.port);}return buffer.toString();}/*** @see java.lang.Object#toString()*/public String toString() {StringBuffer buffer = new StringBuffer(50);        buffer.append(toURI());return buffer.toString();}    /*** @see java.lang.Object#equals(java.lang.Object)*/public boolean equals(final Object o) {if (o instanceof HttpHost) {// shortcut if we're comparing with ourselvesif (o == this) { return true;}HttpHost that = (HttpHost) o;if (!this.hostname.equalsIgnoreCase(that.hostname)) {return false;}if (this.port != that.port) {return false;}if (!this.protocol.equals(that.protocol)) {return false;}// everything matchesreturn true;} else {return false;}}/*** @see java.lang.Object#hashCode()*/public int hashCode() {int hash = LangUtils.HASH_SEED;hash = LangUtils.hashCode(hash, this.hostname);hash = LangUtils.hashCode(hash, this.port);hash = LangUtils.hashCode(hash, this.protocol);return hash;}}