模板模式和Comparable類

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模板模式中，父類規定好了一些演算法的流程，並且空出一些步驟（方法）留給子類填充

Java的數組類中靜態方法sort()就是一個模板，它空出了一個compareTo的方法，留給子類填充，用來規定什麼是大於、等於和小於

 

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());            }}

結果：

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

模板模式和Comparable類