java.util.Collections ---- Comparator ---- Comparable

package com.itheima.demo05.Collections;

public class Student {
    private String name;
    private int age;

    public Student() {
    }

    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", 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;
    }
}

---

com.itheima.demo05.Collections Package; 

Import of java.util.ArrayList; 
Import java.util.Collections; 
Import java.util.Comparator; 

/ * 
    - java.utils.Collections is a collection of tools for the collection operation. Part follows: 
        public static <T> void Sort (List <T> List, Comparator <Super T?>): The set of elements according to an specified rules. The difference Comparator and Comparable 
        Comparable: own (this) and others (parameters) comparison, they need to implement the Comparable interface, rewrite the rules of comparison compareTo method 
        Comparator: find the equivalent of a third-party referee to compare two 
    Comparator collations: 
        o1-o2: ascending order 
 * / 
public class Demo03Sort { 
    public static void main (String [] args) { 
        the ArrayList <Integer> = new new list01 the ArrayList <> ();

     

        list01.add (. 1); 
        list02.add (new Student ( "B Yang Mi"18)); 
        list01.add (. 3);
        list01.add (2); 
        System.out.println (list01); // [. 1,. 3, 2] 

        the Collections.sort (list01, new new Comparator <Integer> () { 
            // Comparative rewrite rules 
            @Override 
            public int Compare (O1 Integer, Integer O2) { 
                // return O1-O2; // ascending 
                return o2-o1; // descending 
            } 
        }); 

        System.out.println (list01); 

        the ArrayList <Student> = new new list02 the ArrayList <> (); 
        list02.add (new new Student ( "A Dilly Reba", 18 is)); 
        list02.add (new new Student ( "Gülnezer Bextiyar", 20 is)); 
        list02.add (new new Student ( "Yang Mi" ,. 17)); 
        System.out.println (list02);

        /*Collections.sort(list02, new new Comparator <Student> () { 
            @Override 
            public int Compare (Student O1, O2 Student) { 
                // ascending order according to age 
                return o1.getAge () - o2.getAge (); 
            } 
        } ); * / 

        // expansion: understanding 
        the Collections.sort (list02, new new Comparator <Student> () { 
            @Override 
            public int Compare (Student O1, O2 Student) { 
                // ascending order according to age 
                int result = o1.getAge () -o2.getAge (); 
                // if two people of the same age, then use the name of the first word comparator 
                IF (Result == 0) { 
                    Result = o1.getName () the charAt (0) -o2.getName (). .charAt (0);
                }
                return  result;
            }

        });

        System.out.println(list02);
    }
}