1.让对象所在的类，实现Comparable接口

2.方法重写compareTo();

3.完成比较规则的制定

对象比较

根据age去比

public class Person implements  Comparable {
    String name;
    int age;
    double salary;

    public Person() {
    }

    public Person(String name, int age, double salary) {
        this.name = name;
        this.age = age;
        this.salary = salary;
    }

    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;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

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

    @Override
    public int compareTo(Object o) {
        Person p2 = (Person)o;
        return this.age-p2.age;
    }
}

public class Test {
    public static void main(String[] args) {
        Person  p1 = new Person("李白",20,999.9);
        Person  p2 = new Person("杜甫",30,999.8);
        int i = p1.compareTo(p2);
        System.out.println(i);
        
    }
}

根据薪水去比

package com.atguigu.Compare.c1;

public class Person implements  Comparable {
    String name;
    int age;
    double salary;

    public Person() {
    }

    public Person(String name, int age, double salary) {
        this.name = name;
        this.age = age;
        this.salary = salary;
    }

    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;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

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

    @Override
    public int compareTo(Object o) {
        Person p = (Person)o;
        if (this.salary>p.salary){
            return 1;
        }else if(this.salary<p.salary){
            return  -1;
        }else{
            return 0;
        }
        //return  Double.compare(this.salary, p.salary);
    }


}

public class Test {
    public static void main(String[] args) {
        Person  p1 = new Person("李白",20,999.9);
        Person  p2 = new Person("杜甫",30,999.8);
        int i = p1.compareTo(p2);
        System.out.println(i);

    }
}

数组比较

按照薪资比较

import com.atguigu.innerclass.in4.exer.Emplyee;

public class Employee implements  Comparable{
    int id;
    String name;
    double salary;

    public Employee() {
    }

    public Employee(int id, String name, double salary) {
        this.id = id;
        this.name = name;
        this.salary = salary;
    }

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

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    @Override
    public int compareTo(Object o) {
        Employee e = (Employee)o;
        /*按照薪资比较*/
        return Double.compare(this.salary, e.salary);
    }
}

import com.atguigu.innerclass.in4.exer.Emplyee;

import java.util.concurrent.ForkJoinPool;

public class Test {
    public static void main(String[] args) {
        Employee e1 = new Employee(1,"张三",9999.9);
        Employee e2 = new Employee(6,"李四",9999.1);
        Employee e3 = new Employee(3,"王五",9999.3);
        Employee e4 = new Employee(4,"赵六",9999.6);
        Employee e5 = new Employee(2,"陈七",9999.8);
        Employee [] es = {e1,e2,e3,e4,e5};
        /*利用冒泡排序*/
        for (int i =0;i<es.length-1;i++){
            for(int j=0;j<es.length-1-i;j++){
                if (es[j].compareTo(es[j + 1])>0) {
                            Employee temp = es[j];
                            es[j]=es[j+1];
                            es[j+1] = temp;
                    }
                }
            }
        for (Employee ele : es){
            System.out.println(ele);
        }

        }
    }

薪资相同时候，按照id比

只需要修改Comparable的重写方法：compareTo

    public int compareTo(Object o) {
        Employee e = (Employee)o;
        /*薪资相同，按照id比较*/
        if(this.salary==e.salary){
            return this.id - e.id;
        }
        return Double.compare(this.salary, e.salary);
    }

数组通用工具类比较

冒泡排序换为，也需要重写compareTo方法，制定比较规则。

 Arrays.sort(es);