Java 模拟 Comparator接口 策略模式

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