Java-马士兵设计模式学习笔记-策略模式-模拟 Comparator接口

续上一篇  《Java 模拟 Comparable接口》

一、Teacher类及Student类的比较大小方式是不固定的，比如老师除了比较职称外，还可比较工龄大小，年龄大小等。则定义Comparator接口，不同比较方法去定义为一个xxComparator类，去实现Comparator接口，Teacher类及Student类引用具体的xxComparator比较器，则可实现灵活的比较方式切换。此则为策略模式的一个例子：当我要比较大小的时候，先定义一个比较器Comparator，但具体的比较由具体的比较策略去实现，如TeacherAgeComparator

PS:解决的问题一涉及要求灵活多变，可扩展等进，则应重点考虑使用多态思想。

 

二、有如下几个类:

1.DataSorter.java

2.Studnet.java

3.Teacher.java

4.Comparable.java

5.Comparator.java

6.TeacherAgeComparator.java

7.StudentMarkComparaotr.java

 

1.DataSorter.java(和上一篇一样)

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.Studnet.java

public class Student implements Comparable<Student> {



	private int mark;

	private Comparator<Student> comparator = new StudentMarkComparator();



	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) {

		return comparator.compare(this, o);

	}

}

　　

3.Teacher.java

public class Teacher implements Comparable<Teacher> {



	private int title;

	private int age;

	private Comparator<Teacher> comparator = new TeacherAgeComparator();

	

	public int getAge() {

		return age;

	}



	public void setAge(int age) {

		this.age = age;

	}





	public Teacher(int age) {

		super();

		this.age = age;

	}

	

	public int getTitle() {

		return title;

	}



	public void setTitle(int title) {

		this.title = title;

	}



	@Override

	public int compareTo(Teacher o) {

		return comparator.compare(this, o);

	}

	

	@Override

	public String toString() {

		return "teacher--" +age+" ";

	}

}

　　

4.Comparable.java

public interface Comparable<T> {

	public int compareTo(T o);

}

　　

5.Comparator.java

public interface Comparator<T> {



	int compare(T o1, T o2);



}

　　

6.TeacherAgeComparator.java

public class TeacherAgeComparator implements Comparator<Teacher> {



	@Override

	public int compare(Teacher o1, Teacher o2) {

		if(o1.getAge() > o2.getAge()){

			return 1;

		}else if(o1.getAge() == o2.getAge()){

			return 0;

		}else{

			return -1;

		}

	}

	

}

　　

7.StudentMarkComparaotr.java

public class StudentMarkComparator implements Comparator<Student> {



	@Override

	public int compare(Student o1, Student o2) {

		if(o1.getMark() > o2.getMark())	return 1;

		else if(o1.getMark() == o2.getMark())	return 0;

		else	return -1;

	}



}

　　

8.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