HashSet 对对象去重

import java.util.Set ;
import java.util.HashSet ;
class Person{
	private String name ;
	private int age ;
	public Person(String name,int age){
		this.name = name ;
		this.age = age ;
	}
	public boolean equals(Object obj){	// 覆写equals，完成对象比较
		if(this==obj){
			return true ;
		}
		if(!(obj instanceof Person)){
			return false ;
		}
		Person p = (Person)obj ;	// 向下转型
		if(this.name.equals(p.name)&&this.age==p.age){
			return true ;
		}else{
			return false ;
		}
	}
	public int hashCode(){
		return this.name.hashCode() * this.age	; // 定义一个公式
	}
	public String toString(){
		return "姓名：" + this.name + "；年龄：" + this.age ;
	}
};
public class RepeatDemo02{
	public static void main(String args[]){
		Set<Person> allSet = new HashSet<Person>() ;
		allSet.add(new Person("张三",30)) ;
		allSet.add(new Person("李四",31)) ;
		allSet.add(new Person("王五",32)) ;
		allSet.add(new Person("王五",32)) ;
		allSet.add(new Person("王五",32)) ;
		allSet.add(new Person("赵六",33)) ;
		allSet.add(new Person("孙七",33)) ;
		System.out.println(allSet) ;
	}
};

 对对象去重

 

 

 

 

TreeSet 排序

 

 

import java.util.Set ;
import java.util.TreeSet ;
class Person implements Comparable<Person>{
	private String name ;
	private int age ;
	public Person(String name,int age){
		this.name = name ;
		this.age = age ;
	}
	public String toString(){
		return "姓名：" + this.name + "；年龄：" + this.age ;
	}
	public int compareTo(Person per){
		if(this.age>per.age){
			return 1 ;
		}else if(this.age<per.age){
			return -1 ;
		}else{
			return this.name.compareTo(per.name) ;	// 调用String中的compareTo()方法
		}
	}
};
public class TreeSetDemo04{
	public static void main(String args[]){
		Set<Person> allSet = new TreeSet<Person>() ;
		allSet.add(new Person("张三",30)) ;
		allSet.add(new Person("李四",31)) ;
		allSet.add(new Person("王五",32)) ;
		allSet.add(new Person("王五",32)) ;
		allSet.add(new Person("王五",32)) ;
		allSet.add(new Person("赵六",33)) ;
		allSet.add(new Person("孙七",33)) ;
		System.out.println(allSet) ;
	}
};