HashSet简单示例

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package cn.itcast.demo;import java.util.HashSet;import java.util.Iterator;import java.util.LinkedHashSet; class Student{private int age;private String name;public Student(int age,String name){this.age = age;this.name = name;}//要显示Student类的信息，必须重写toString 方法public String toString(){return   "age :"+age+"  name:"+name;}public int hashCode(){return age*name.hashCode();}public boolean equals(Object o){Student s = (Student) o;return age == s.age && name.equalsIgnoreCase(s.name);}}public class HashSetTest {public static void main(String[] args) {// TODO Auto-generated method stub //添加的String对象,不需要进行重写------------------------------HashSet hs1 = new HashSet();hs1.add("zxx"); hs1.add("zahx");hs1.add("zyj");hs1.add("xmh");hs1.add("zah");Iterator it =  hs1.iterator();while(it.hasNext()){System.out.println(it.next());}//-----------------------------------------------------//如果添加的是一个自定的对象-------------------------------------HashSet hs = new HashSet();hs.add(new Student(28,"zah"));hs.add(new Student(31,"xmh"));hs.add(new Student(30,"zyj"));hs.add(new Student(28,"zah"));hs.add(new Student(33,"zxx"));Student a1 = new Student(34,"dxx");Student a11 = new Student(35,"dxx");System.out.println("a1code"+a1.hashCode());System.out.println("a11code"+a11.hashCode());//--------------------------心血来潮的一个测试String str1 ="abc";String str2 ="abc";System.out.println("str1"+str1.hashCode());System.out.println("str2"+str2.hashCode());//-------------------------------------hs.add(null);hs.add(null);Iterator it1 = hs.iterator();while(it1.hasNext()){System.out.println(it1.next());}//-----------------------------------------------------LinkedHashSet linkHashSet =  new LinkedHashSet();Student linkedstu1 = new Student();linkHashSet.add(linkedstu1);}}

测试发现HashSet添加的时候无序，而且不能重复加入

运行效果如图：

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