List集合按某个字段排序（Collections.sort）

package wjtest_01;

import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; import java.util.List;

public class ListSort<E> { @SuppressWarnings("unchecked") public static void main(String[] args) {

	List<Student> list = new ArrayList<Student>();

	// 创建3个学生对象，年龄分别是20、19、21，并将他们依次放入List中
	Student s1 = new Student();
	s1.setAge(20);
	s1.setUsable(true);
	Student s2 = new Student();
	s2.setAge(19);
	s2.setUsable(true);
	Student s3 = new Student();
	s3.setAge(21);
	s3.setUsable(false);
	list.add(s1);
	list.add(s2);
	list.add(s3);

	System.out.println("排序前：" + list);

  Collections.sort(list, new Comparator<Student>() {```

  	@Override
  	public int compare(Student o1, Student o2) {
  		// 按照学生的年龄进行升序排列
  		if (o1.getAge() > o2.getAge()) {
  			return 1;
  		}
  		if (o1.getAge() == o2.getAge()) {
  			return 0;
  		}
  		return -1;
  	}
  });

		System.out.println("升序排序后：" + list);

> 	Collections.sort(list, new Comparator<Student>() {
> 
> 			public int compare(Student o1, Student o2) {
> 
> 				// 按照学生的年龄进行降序排列
> 				if (o1.getAge() > o2.getAge()) {
> 					return -1;
> 				}
> 				if (o1.getAge() == o2.getAge()) {
> 					return 0;
> 				}
> 				return 1;
> 			}
> 		});

		System.out.println("降序排序后：" + list);

		Boolean b1 = true; // 创建Boolean对象1

		Boolean b2 = false; // 创建Boolean对象0

		Boolean b3 = true; // 创建Boolean对象1
		System.out.println(b1);

		int i;

		i = b1.compareTo(b2); // b1和b2进行比较  

		System.out.println(i);//1-0 

		i = b2.compareTo(b1); // b2和b1进行比较

		System.out.println(i);//0-1

		i = b1.compareTo(b3); // b1和b3进行比较

		System.out.println(i);//1-1
	}
}

class Student{  
    
    private int age;
    
    private Boolean isUsable;

	public int getAge() {  
        return age;  
    }  
  
    public Boolean isUsable() {
		return isUsable;
	}

	public void setUsable(Boolean isUsable) {
		this.isUsable = isUsable;
	}

	public void setAge(int age) {  
        this.age = age;  
    }  
    @Override  
    public String toString() {  
        return getAge()+"";  
    }  
}
转载自：https://blog.csdn.net/wangjuan_01/article/details/51351633
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