package 计算机挑战赛国赛;

import java.util.ArrayList;
import java.util.Collections;

public class test8 {

    static class student implements Comparable<student>{
        String name;
        int age;
        student(String name,int age){
            this.name=name;
            this.age=age;
        }

        @Override
        public int compareTo(student o) {
            return this.age-o.age;
        }
    }

    public static void main(String[] args) {
        ArrayList<student> list = new ArrayList<student>();
        list.add(new student("zhangsan",22));
        list.add(new student("husheng",20));
        list.add(new student("lisi",25));
        Collections.sort(list);
        for (student student : list) {
            System.out.println(student.name+" "+student.age);
        }
    }
}

输出：
husheng 20
zhangsan 22
lisi 25

package 计算机挑战赛国赛;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;

public class test8 {

    static class student {
        String name;
        int age;
        student(String name,int age){
            this.name=name;
            this.age=age;
        }

    }

    public static void main(String[] args) {
        student[] arr = new student[3];
        arr[0]=new student("zhangsan",22);
        arr[1]=new student("husheng",20);
        arr[2]=new student("lisi",25);
        Arrays.sort(arr,0,3,(o1,o2)->o1.age-o2.age);
        //如果o1.age或者o2.age为浮点型的话，应改为(int)(o1.age-o2.age)，将其转化为整形
        //也可以将o1.age和o2.age扩大整数倍，使其变成整数。如(int)(o1.age*100-o2.age*100)
        for (student student : arr) {
            System.out.println(student.name+" "+student.age);
        }
    }
}

输出：
husheng 20
zhangsan 22
lisi 25