Comparable接口

Comparable接口实际上属于比较器的操作接口，定义如下：

public interface Comparable<T>{ 

//接口上使用了泛型

 int compareTo(T o); //定义compareTo方法，此方法完成排序

}

compareTo（）方法的三种返回值类型：

小于：-1

等于：0

大于：1

1 package com.fwj.compare; 2  3 public class Student implements Comparable
     
       { 4  5     private String name; 6     private int age; 7     private int score; 8      9     public Student(String name, int age, int score) {10         super();11         this.name = name;12         this.age = age;13         this.score = score;14     }15 16     @Override17     public String toString() {18         return "Student [name=" + name + ", age=" + age + ", score=" + score19                 + "]";20     }21 22     @Override23     public int compareTo(Student stu) {    //按成绩升序排序，如果成绩相同按年龄升序排序24 25         if(this.score>stu.score){26             return 1;27         }else if(this.score
      
       stu.age){31                 return 1;32             }else if(this.age
      
     

运行结果：

1 =================排序前=================== 2 Student [name=fwj, age=23, score=90] 3 Student [name=hpf, age=26, score=83] 4 Student [name=wh, age=25, score=83] 5 Student [name=lw, age=20, score=86] 6 =================排序后=================== 7 Student [name=wh, age=25, score=83] 8 Student [name=hpf, age=26, score=83] 9 Student [name=lw, age=20, score=86]10 Student [name=fwj, age=23, score=90]

Comparator接口

如果一个类已经开发完成，则肯定不能修改，所以，此时为了让此类具有排序功能，可以使用comparator完成排序的操作。

1 package com.fwj.compare; 2  3 public class Student { 4  5     private String name; 6     private int age; 7     private int score; 8      9     public String getName() {10         return name;11     }12 13     public void setName(String name) {14         this.name = name;15     }16 17     public int getAge() {18         return age;19     }20 21     public void setAge(int age) {22         this.age = age;23     }24 25     public int getScore() {26         return score;27     }28 29     public void setScore(int score) {30         this.score = score;31     }32 33     public Student(String name, int age, int score) {34         super();35         this.name = name;36         this.age = age;37         this.score = score;38     }39 40     @Override41     public boolean equals(Object obj) {
   //复写equals，完成对象比较42 43         if(this==obj){44             return true;45         }46         if(!(obj instanceof Student)){47             return false;48         }49         Student stu = (Student)obj;50         if(this.name==stu.name&&this.age==stu.age&&this.score==stu.score){51             return true;52         }else{53             return false;54         }55     }56 57     @Override58     public String toString() {59         return "Student [name=" + name + ", age=" + age + ", score=" + score60                 + "]";61     }62 63 }

1 package com.fwj.compare; 2  3 import java.util.Comparator; 4  5 public class StudentComparetor implements Comparator
     
       { 6  7     @Override 8     public int compare(Student stu1, Student stu2) { 9         if(stu1.getScore()>stu2.getScore()){10             return -1;11         }else if(stu1.getScore()
      
       stu2.getAge()){15                 return -1;16             }else if(stu1.getAge()
      
     

1 package com.fwj.compare; 2  3 import java.util.Arrays; 4  5 public class Test { 6  7     public static void main(String[] args) { 8          9         Student stu[] = {
   new Student("fwj",23,90),10                 new Student("hpf",26,83),11                 new Student("wh",25,83),12                 new Student("lw",20,86)13         };14         System.out.println("=================排序前===================");15         print(stu);16         System.out.println("=================排序后===================");17         Arrays.sort(stu, new StudentComparetor());18         print(stu);19     }20     public static void print(Student stu[]){21     22         for (Student student : stu) {23             System.out.println(student);24         }25     }26 27 }

 运行结果：

1 =================排序前=================== 2 Student [name=fwj, age=23, score=90] 3 Student [name=hpf, age=26, score=83] 4 Student [name=wh, age=25, score=83] 5 Student [name=lw, age=20, score=86] 6 =================排序后=================== 7 Student [name=fwj, age=23, score=90] 8 Student [name=lw, age=20, score=86] 9 Student [name=hpf, age=26, score=83]10 Student [name=wh, age=25, score=83]