Java-马士兵设计模式学习笔记-策略模式-模拟Comparable接口

一、情况

1.目标：要在专门用于排序数据的DataSorter.java中实现对所有A类，B类，C类，D类等等的排序

2.初步想法：DataSorter.java的代码如下

 

public class DataSorter {



	public static void sort(A a){

		

	}

	

	public static void sort(B a){

		

	}

	

	public static void sort(C c){

		

	}

	

	//...................

}

 

　　

3.这样会造成DataSorter的可扩展性差，要支持对新类的排序时，要修改代码。更好的思路是：既然DataSorter是要根据不同的类的采取不同的方法实现排序，那么具体实现排序的方法交由子类去实现，且都实现同一个接口Comparable，那么DataSorter只需对Comparable排序，而无需理会具体要排序的是什么类(多态)

4.有如下几个类：

(1)DataSorter.java

(2)接口Comparable.java

(3)Student.java

(4)Teacher.java

(5)Test.java

 

 

5.代码如下：

(1)DataSorter.java

public class DataSorter {



	public static void sort(Comparable [] a) {

		

		int index;							//保存每次比较,最大值的下标;

		

		for(int i = 1; i < a.length; i++){	//控制外循环次数

			index = 0;

			for(int j = 1; j <= a.length - i ; j++){

				if(a[j].compareTo(a[index]) == 1){

					index = j;

				}

			}

			swap(a, index, a.length -i);

		}

	}





	private static void swap(Comparable[] a, int x, int y) {

		Comparable tmp = a[x];

		a[x] = a[y];

		a[y] = tmp;

		

	}

	

	

	//输出数组元素

	public static void show(Comparable[] a) {

		for(int i = 0; i < a.length; i++){

			System.out.println(a[i]);

		}

	}



}

　　

(2)Comparable.java

public interface Comparable<T> {

	public int compareTo(T o);

}

　　

(3)Teacher.java

public class Teacher implements Comparable<Teacher> {



	private int title;

	

	public Teacher(int title) {

		super();

		this.title = title;

	}



	public int getTitle() {

		return title;

	}



	public void setTitle(int title) {

		this.title = title;

	}



	@Override

	public int compareTo(Teacher o) {

		if(this.title > o.getTitle()){

			return 1;

		}else if(this.title == o.getTitle()){

			return 0;

		}else{

			return -1;

		}

	}

	

	@Override

	public String toString() {

		return "teacher--" +title+" ";

	}

}

　　

(4)Student.java

public class Student implements Comparable<Student> {



	private int mark;



	public int getMark() {

		return mark;

	}



	public void setMark(int mark) {

		this.mark = mark;

	}



	public Student(int mark) {

		super();

		this.mark = mark;

	}

	

	@Override

	public String toString() {

		return "student" +mark+" ";

	}



	@Override

	public int compareTo(Student o) {

		if(this.mark > o.getMark()){

			return 1;

		}else if(this.mark == o.getMark()){

			return 0;

		}else{

			return -1;

		}

	}

}

　　

(5)Test.java

public class Test {



	public static void main(String[] args) {

		//int [] a = {9,2,1,8,0,3};

		Student [] ss = {new Student(59),new Student(30),new Student(90)};

		DataSorter.sort(ss);

		DataSorter.show(ss);

		

		Teacher [] ts = {new Teacher(10),new Teacher(3),new Teacher(12)};

		DataSorter.sort(ts);

		DataSorter.show(ts);

		

	}



}

　　

测试结果