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java 对象比较常见的两种方法

方法一：对象实现Compareable方法

package com.imooc.appoint.map;

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

class Student implements Comparable{

    String name;
    int age;
    int score;

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

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

}

public class Test {

    public static void main(String[] args) {
        ArrayList students = new ArrayList<>();
        students.add(new Student("大铭", 19, 89));
        students.add(new Student("来福", 26, 90));
        students.add(new Student("仓颉", 23, 70));
        students.add(new Student("王磊", 18, 80));

        System.out.println("排序前:");
        for (Student student : students) {
            System.out.println("姓名："+student.name+" 年龄："+student.age+" 成绩："+student.score);
        }

// 排序
        Collections.sort(students);

        System.out.println("排序后:");
        for (Student student : students) {
            System.out.println("姓名："+student.name+" 年龄："+student.age+" 成绩："+student.score);
        }
    }
}

方法二：传入比较器Compartor

方法二：使用Comparator匿名内部类实现。

还是使用同一个例子，按成绩将学生排序：

/**
* 学生类
*/
class Student {

String name;
int age;
int score;

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

public class Test {

public static void main(String[] args) {
// TODO Auto-generated method stub
ArrayList students = new ArrayList<>();
students.add(new Student("大铭", 19, 89));
students.add(new Student("来福", 26, 90));
students.add(new Student("仓颉", 23, 70));
students.add(new Student("王磊", 18, 80));

System.out.println("排序前:");
for (Student student : students) {
System.out.println("姓名："+student.name+" 年龄："+student.age+" 成绩："+student.score);
}

Collections.sort(students,new Comparator() {

@Override
public int compare(Student o1, Student o2) {
// TODO Auto-generated method stub
return o1.age-o2.age;
}
});

System.out.println("排序后:");
for (Student student : students) {
System.out.println("姓名："+student.name+" 年龄："+student.age+" 成绩："+student.score);
}
}
}

3、判断对象是否相同的