Java 集合学习<1>HashSet
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package cn.iworker.collection;import java.util.HashSet;import java.util.Iterator;import org.omg.PortableInterceptor.Interceptor;/** * @desc <pre></pre> * 1.HashSet的底层是HashMap来实现的 * 2.当使用add()方法将对象添加到HashSet中的时候,实际上是该对象作为底层的HashMap的Key加入到集合中,HashMap的值插入一个空对象。 * @author Weiliang Hu * @Date 2013-10-24 */public class HashSetTest {public static void main(String[] args) {HashSet<Object> mHashSet = new HashSet<Object>();mHashSet.add("a");mHashSet.add("b");mHashSet.add("c");mHashSet.add("d");mHashSet.add("a");Iterator interator = mHashSet.iterator();System.out.println("while hasNext:");while (interator.hasNext()) {String str = (String) interator.next();System.out.println(str);}System.out.println("for:");for (Iterator mIter = mHashSet.iterator(); mIter.hasNext();) {System.out.println(mIter.next());}mHashSet.clear();mHashSet.add(new String("a"));mHashSet.add(new String("b"));mHashSet.add(new String("a"));System.out.println(mHashSet);//输出结果是[b, a]mHashSet.clear();mHashSet.add(new User("zhangsan"));mHashSet.add(new User("lisi"));mHashSet.add(new User("zhangsan"));System.out.println(mHashSet);//[cn.iworker.collection.User@3e0ebb, cn.iworker.collection.User@39443f, cn.iworker.collection.User@19836ed]}}class User {String name;public User(String name) {this.name = name;}}