HashSet

package ch3;public class Student {    private int age;    private String name;    Student(int num,String name)    {    this.age =num;    this.name =name;    }@Overridepublic boolean equals(Object o) {// TODO Auto-generated method stubStudent s =(Student)o;return  age ==s.age&&name.equals(s.name);}@Overridepublic int hashCode() {// TODO Auto-generated method stubreturn age*name.hashCode();}@Overridepublic String toString() {// TODO Auto-generated method stubreturn "age:" +age+"name:"+name;}    }

package ch3;import java.util.HashSet;import java.util.Iterator;public class HashSetText1 {public static void main(String[] args) {// TODO Auto-generated method stubHashSet hs = new HashSet();hs.add(new Student(28,"zhang"));hs.add(new Student(21,"zhang"));hs.add(new Student(28,"li"));hs.add(new Student(28,"zhao"));hs.add(new Student(28,"zhang"));//HashSet不能重复，无序    hs.add(null);Iterator in = hs.iterator();while(in.hasNext()){System.out.println(in.next());}}}