模板模式和Comparable类

模板模式中，父类规定好了一些算法的流程，并且空出一些步骤（方法）留给子类填充

Java的数组类中静态方法sort()就是一个模板，它空出了一个compareTo的方法，留给子类填充，用来规定什么是大于、等于和小于

package com.example.template;

public class Duck implements Comparable<Duck>{

    private String name;
    private int weight;

    public Duck(String name, int weight){
        this.name = name;
        this.weight = weight;
    }

    public String toString(){
        return "name" + name + "weight" + weight;
    }

    @Override
    public int compareTo(Duck other) {

        if(this.weight < other.weight){
            return -1;
        }else if(this.weight > other.weight){
            return 1;
        }
        return 0;
    }
}

package com.example.template;

import java.util.Random;

public class Employee implements Comparable<Employee> {

    private String name;
    private int id;
    private double salary;

    public Employee(String name, double salary){
        this.name = name;
        this.salary = salary;
        Random ra = new Random();
        this.id = ra.nextInt(1000000);
    }

    public String toString(){
        return "name:" + name + " salary:" + salary + " ElyId:" + id;
    }

    @Override
    public int compareTo(Employee other) {
        if(this.id < other.id){
            return -1;
        }else if(this.id > other.id){
            return 1;
        }
        return 0;
    }

}

package com.example.template;

import java.util.Arrays;

public class Test {

    public static void main(String[] args)
    {
        Duck[] ducks = new Duck[4];

        ducks[0] = new Duck("Jason", 89);
        ducks[1] = new Duck("Amemle", 100);
        ducks[2] = new Duck("Mike", 72);
        ducks[3] = new Duck("Ham", 102);

        System.out.println("before sort:");
        for(int i = 0 ; i < ducks.length ; i++)
            System.out.println(ducks[i].toString());

        Arrays.sort(ducks);

        System.out.println("after sort:");
        for(int i = 0 ; i < ducks.length ; i++)
            System.out.println(ducks[i].toString());

        Employee[] emps = {
            new Employee("Jason", 999.0),
            new Employee("Canson", 1599.1),
            new Employee("Jack", 887.9)
        };

        System.out.println("--------------------");

        System.out.println("before sort:");
        for(int i = 0 ; i < emps.length ; i++)
            System.out.println(emps[i].toString());

        Arrays.sort(emps);

        System.out.println("after sort:");
        for(int i = 0 ; i < emps.length ; i++)
            System.out.println(emps[i].toString());

    }
}

结果：

before sort:
nameJasonweight89
nameAmemleweight100
nameMikeweight72
nameHamweight102
after sort:
nameMikeweight72
nameJasonweight89
nameAmemleweight100
nameHamweight102
--------------------
before sort:
name:Jason salary:999.0 ElyId:502862
name:Canson salary:1599.1 ElyId:716871
name:Jack salary:887.9 ElyId:552929
after sort:
name:Jason salary:999.0 ElyId:502862
name:Jack salary:887.9 ElyId:552929
name:Canson salary:1599.1 ElyId:716871