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