How to sort objects of a class in java

We need to sort the objects of the class according to a certain attribute (or multiple attributes) in the class. There are two ways to achieve this. One method is class implementation. Comparable8742468051c85b06f0a0af9e3e506b5c interface, and then call the Collections.sort(List) method to sort. The other method is that the class does not implement the Comparable8742468051c85b06f0a0af9e3e506b5c interface, When sorting, use the Collections.sort(List, Comparator8742468051c85b06f0a0af9e3e506b5c) method and implement the Comparator8742468051c85b06f0a0af9e3e506b5c interface.

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First create a simple student class:

public class Student {
    
    private String name;
    
    private int age;
 
    public Student() {}
 
    public Student(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;
    }
}

1. Implement Comparable

public class Student implements Comparable<Student>{
 
    private String name;
 
    private int age;
 
    public Student() {}
 
    public Student(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;
    }
 
    /**
     * 将对象按姓名字典序升序排序
     * @param o
     * @return
     */
    @Override
    public int compareTo(Student o) {
        return this.name.compareTo(o.getName());
    }
 
    @Override
    public String toString() {
        return "Student{" +
                "name=&#39;" + name + &#39;\&#39;&#39; +
                ", age=" + age +
                &#39;}&#39;;
    }
}

2. Sort by implementing the Comparable8742468051c85b06f0a0af9e3e506b5c interface in the Collections.sort() method

public class Client {
 
    public static void main(String[] args){
        List<Student> students = new ArrayList<>();
        students.add(new Student("a", 18));
        students.add(new Student("c", 19));
        students.add(new Student("b", 20));
 
        Collections.sort(students, new Comparator<Student>() {
            @Override
            public int compare(Student o1, Student o2) {
                return o1.getAge()>o2.getAge()? -1:(o1.getAge()==o2.getAge()? 0:1);
            }
        });
        for(Student student:students){
            System.out.println(student.toString());
        }
    }
 
}

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