Collections.sort

 

 

   Java 基础小知识： Collections.sort() 方法的使用：

  （参考网上的例子）

 

  1 、 User类

public class User implements Comparable<User>{

	private String name;
	private Integer order;
	
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Integer getOrder() {
		return order;
	}
	public void setOrder(Integer order) {
		this.order = order;
	}
	@Override
	public int compareTo(User o) {
		return this.getOrder().compareTo(o.getOrder());
	}

}

     Test:

 

public class Test {

	public static void main(String[] args) {
		User user1 = new User();
		user1.setName("aaa");
		user1.setOrder(2);
		
		User user2 = new User();
		user2.setName("bbb");
		user2.setOrder(1);
		
		List<User> list = new ArrayList<User>();
		list.add(user1);
		list.add(user2);
		
		Collections.sort(list);
		
		for(User u : list){
			System.out.println(u.getOrder()+"--->"+u.getName());
		}
	}
}

 

 

 

2、另一种方式

 

   User 类

 

 

public class User {

	private String name;
	private Integer order;
	private Integer count;
	
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Integer getOrder() {
		return order;
	}
	public void setOrder(Integer order) {
		this.order = order;
	}
	public Integer getCount() {
		return count;
	}
	public void setCount(Integer count) {
		this.count = count;
	}
	
}

 

   Test类：

 

public class Test {

	public static void main(String[] args) {
		 
		User user1 = new User();
		user1.setName("aaa");
		user1.setOrder(2);
		user1.setOrder(30);
		
		User user2 = new User();
		user2.setName("bbb");
		user2.setOrder(1);
		user2.setCount(40);
		
		User user3 = new User();
		user3.setName("ccc");
		user3.setOrder(1);
		user3.setCount(50);
		
		List<User> list = new ArrayList<User>();
		list.add(user1);
		list.add(user2);
		list.add(user3);
		
		Collections.sort(list ,new Comparator<User>() {
			@Override
			public int compare(User o1, User o2) {
				int i = o1.getOrder().compareTo(o2.getOrder());
				if(i==0){
					return o2.getCount().compareTo(o1.getCount());
				}else{
					return i;
				}
			}
		});
		
		for(User u : list){
			System.out.println(u.getOrder()+"--->"+u.getName());
		}
	}
}

 

 

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