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<Student> { 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 @Override 17 public String toString() { 18 return "Student [name=" + name + ", age=" + age + ", score=" + score 19 + "]"; 20 } 21 22 @Override 23 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.score){ 28 return -1; 29 }else{ 30 if(this.age>stu.age){ 31 return 1; 32 }else if(this.age<stu.age){ 33 return -1; 34 }else{ 35 return 0; 36 } 37 } 38 } 39 40 } 41 42 43 package com.fwj.compare; 44 45 import java.util.Arrays; 46 47 public class Test { 48 49 public static void main(String[] args) { 50 51 Student stu[] = {new Student("fwj",23,90), 52 new Student("hpf",26,83), 53 new Student("wh",25,83), 54 new Student("lw",20,86) 55 }; 56 System.out.println("=================排序前==================="); 57 print(stu); 58 System.out.println("=================排序后==================="); 59 Arrays.sort(stu); 60 print(stu); 61 } 62 public static void print(Student stu[]){ 63 64 for (Student student : stu) { 65 System.out.println(student); 66 } 67 } 68 69 }
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 @Override 41 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 @Override 58 public String toString() { 59 return "Student [name=" + name + ", age=" + age + ", score=" + score 60 + "]"; 61 } 62 63 }
1 package com.fwj.compare; 2 3 import java.util.Comparator; 4 5 public class StudentComparetor implements Comparator<Student> { 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.getScore()){ 12 return 1; 13 }else{ 14 if(stu1.getAge()>stu2.getAge()){ 15 return -1; 16 }else if(stu1.getAge()<stu2.getAge()){ 17 return 1; 18 }else{ 19 return 0; 20 } 21 } 22 } 23 24 //貌似实体类中复写了equals方法，此类中就不需要再次复写，，，，？？？？？ 25 @Override 26 public boolean equals(Object obj) { 27 // TODO Auto-generated method stub 28 return this.equals(obj); 29 } 30 31 }
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]