java Collections.sort应用

1.给字符串list排序

public static void main(String args[]){
			
		List<String> list=new ArrayList<String>();
		list.add("e");
		list.add("c");
		list.add("g");
		list.add("f");
		
		System.out.println(">>>>>>>>>>>>>排序前:>>>>>>>>>>>>>");
		
		for(String str:list)
			System.out.println(str);
		
		System.out.println(">>>>>>>>>>>>>排序后:>>>>>>>>>>>>>");
		
		Collections.sort(list);
		
		for(String str:list)
			System.out.println(str);
		
	}

>>>>>>>>>>>>>排序前:>>>>>>>>>>>>>
e
c
g
f
>>>>>>>>>>>>>排序后:>>>>>>>>>>>>>
c
e
f
g

2.给对象排序 对象需要实现Comparable接口，重写compareTo函数

package testsort;


public class Entity implements Comparable<Entity>{
	private String name;
	private int age;
	public Entity(String name,int age){
		this.name=name;
		this.age=age;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	@Override
	public int compareTo(Entity entity) {
		// TODO Auto-generated method stub
		if(this.age>entity.age){
			return 1;
		}else if(this.age<entity.age){
			return -1;
		}else{
			if(this.name.hashCode()>entity.name.hashCode()){
				return 1;
			}else if(this.name.hashCode()<entity.name.hashCode()){
				return -1;
			}else{
				return 0;
			}
		}
	}
}

public static void main(String args[]){
			
		List<Entity> list=new ArrayList<Entity>();
		list.add(new Entity("luffy",19));
		list.add(new Entity("sanji",21));
		list.add(new Entity("sorron",21));
		list.add(new Entity("nami",18));
		
		System.out.println(">>>>>>>>>>>>排序前:>>>>>>>>>>>>>>");
		
		for(Entity e:list){
			System.out.println("name:"+e.getName()+" "+e.getAge());
		}
		
		System.out.println(">>>>>>>>>>>>>排序后:>>>>>>>>>>>>>");
		
		Collections.sort(list);
		
		for(Entity e:list){
			System.out.println("name:"+e.getName()+" "+e.getAge());
		}
		
	}

>>>>>>>>>>>>排序前:>>>>>>>>>>>>>>
name:luffy 19
name:sanji 21
name:sorron 21
name:nami 18
>>>>>>>>>>>>>排序后:>>>>>>>>>>>>>
name:nami 18
name:luffy 19
name:sorron 21
name:sanji 21