HashSet与TreeSet

HashSetpublic class HashSetTest {public static void main(String []args){HashSet hs=new HashSet();/* hs.add("one");hs.add("two");hs.add("three");hs.add("one");*/hs.add(new Student(1,"zhangsan"));hs.add(new Student(2,"lisi"));hs.add(new Student(1,"zhangsan"));hs.add(new Student(3,"wangwu"));Iterator it=hs.iterator();while(it.hasNext()){System.out.println(it.next());}}}class Student{int num;String name;Student(int num,String name){this.name=name;this.num=num;}public int HashCode(){return num*name.hashCode();}public boolean equals(Object o){Student s=(Student)o;return num==s.num && name.equals(s.name);}public String toString(){return "name : ="+name;}}TreeSetimport java.util.*;public class TreeSetTest {//如果自定义类对象要加入TreeSet要实现Comparable接口public static void main(String []args){TreeSet ts=new TreeSet(new Student.StudentComparator());/* ts.add("winsun");ts.add("weixin");ts.add("mybole");*/ts.add(new Student(2,"lisi"));ts.add(new Student(1,"wangwu"));ts.add(new Student(3,"zhangsan"));ts.add(new Student(3,"mybole"));Iterator it=ts.iterator();while(it.hasNext()){System.out.println(it.next());}}}class Student implements Comparable{int num;String name;static class StudentComparator implements Comparator{public int compare(Object o1,Object o2){Student s1=(Student)o1;Student s2=(Student)o2;int result=s1.num>s2.num ? 1 : (s1.num==s2.num ? 0 : -1);if(result==0){ //String类实现了compareTo()方法.result=s1.name.compareTo(s2.name);}return result;}}public static void printElements(Collection c){Iterator it=c.iterator();while(it.hasNext()){System.out.println(it.next());}}Student(int num,String name){this.name=name;this.num=num;}public int HashCode(){return num*name.hashCode();}public boolean equals(Object o){Student s=(Student)o;return num==s.num && name.equals(s.name);}public int compareTo(Object o){Student s=(Student)o;return num>s.num?1:(num==s.num?0:-1);}public String toString(){return num+":"+name;}}