Comparable与Comparator的区别

当需要排序的集合或数组不是单纯的数字型时，通常可以使用Comparator或Comparable,可用以下两种方法进行自定义排序.
两者的共同点都是 返回正数 前者大 负数 后者大  0相等
![文件的目录结构](http://img.blog.csdn.net/20151214225711581)

继承Comparable接口

package com.train.blog;

public class Student implements Comparable<Student> {
private int id;
private int age;
private String name;

Student(int id, int age, String name) {
this.id = id;
this.age = age;
this.name = name;
}

public int getId() {
return id;
}

public int getAge() {
return age;
}

public String getName() {
return name;
}

public void setId(int id) {
this.id = id;
}

public void setAge(int age) {
this.age = age;
}

public void setName(String name) {
this.name = name;
}

@Override
public int compareTo(Student s) {
// TODO Auto-generated method stub
return this.age - s.age;
}
}

继承Comparable接口 进行测试

public void TestComparable(){
List<Student> list=new ArrayList<Student>();
Student student1=new Student(1,10,"名字1");
Student student2=new Student(1,4,"名字2");
Student student3=new Student(1,2,"名字3");
Student student4=new Student(1,20,"名字4");
Student student5=new Student(1,15,"名字5");
list.add(student1);
list.add(student2);
list.add(student3);
list.add(student4);
list.add(student5);
Collections.sort(list);
for (Student student : list) {
System.out.println("student的年龄："+student.getAge()+"  学生的姓名："+student.getName());
}
}

继承Comparator

package com.train.blog;

public class Teacher {
private int id;
private int age;
private String name;

Teacher(int id, int age, String name) {
this.id = id;
this.age = age;
this.name = name;
}

public int getId() {
return id;
}

public int getAge() {
return age;
}

public String getName() {
return name;
}

public void setId(int id) {
this.id = id;
}

public void setAge(int age) {
this.age = age;
}

public void setName(String name) {
this.name = name;
}
}

package com.train.blog;

import java.util.Comparator;

public class TeacherComparator implements Comparator<Teacher> {

@Override
public int compare(Teacher o1, Teacher o2) {
// TODO Auto-generated method stub
return  (o1.getAge()-o2.getAge());
}

}

继承Comparator接口 进行测试

public void TestComparator(){
List<Teacher> list=new ArrayList<Teacher>();
Teacher teacher1=new Teacher(1,10,"名字1");
Teacher teacher2=new Teacher(1,4,"名字2");
Teacher teacher3=new Teacher(1,2,"名字3");
Teacher teacher4=new Teacher(1,20,"名字4");
Teacher teacher5=new Teacher(1,15,"名字5");
list.add(teacher1);
list.add(teacher2);
list.add(teacher3);
list.add(teacher4);
list.add(teacher5);
Collections.sort(list,new TeacherComparator());
for (Teacher teacher : list) {
System.out.println("teacher的年龄："+teacher.getAge()+"  teacher的姓名："+teacher.getName());
}
}

总结

【1】继承Comparable 覆写compareTo 方法; 继承Comparator覆写compare 方法;

【2】Comparable 表明对象之间可以比较,Comparator可以看成一种算法的实现，将算法和数据分离

【3】Comparator使用环境

(1)类的设计师没有考虑到比较问题而没有实现Comparable，可以通过Comparator来实现排序而不必改变对象本身

(2)可以使用多种排序标准，比如升序、降序等