比较器 - Cirry's Blog

比较器的引出Comparable

范例：实现自定义对象数组排序操作

1
package cn.cccc.demo;
2
import java.util.Arrays;
3
public class Demo {
4
    public static void main(String[] args) {
5
       Person data [] = new Person [] {
6
               new Person("cc",20),
7
               new Person("ww",18)
8
       };
9

10
       Arrays.sort(data);
11
       System.out.println(Arrays.toString(data));
12
    }
13
}
14
class Person implements Comparable<Person>{
15
    private String name;
14 collapsed lines
16
    private int age;
17
    public Person(String name , int age){
18
       this.name = name;
19
       this.age = age;
20
    }
21
    public String toString(){
22
       return "[个人信息]姓名"+this.name+"年龄："+this.age;
23
    }
24
    @Override
25
    public int compareTo(Person per) {
26
       // TODO Auto-generated method stub
27
       return per.age-this.age;
28
    }
29
}

Comparator比较器

是一种挽救类的比较器，其主要的目的是解决一些没有使用Comparabnle排序的类的对象数组排序。范例：现在项目已经开发完成了，并且由于先期的设计并没有去考虑到所为的比较器功能。范例：

1
package cn.cccc.demo;
2
import java.util.Arrays;
3
public class Demo {
4
    public static void main(String[] args) {
5
       Person data [] = new Person [] {
6
               new Person("cc",20),
7
               new Person("ww",18)
8
       };
9
    }
10
}
11
class Person{
12
    private String name;
13
    private int age;
14
    public Person(String name , int age){
15
       this.name = name;
6 collapsed lines
16
       this.age = age;
17
    }
18
    public String toString(){
19
       return "[个人信息]姓名"+this.name+"年龄："+this.age;
20
    }
21
}

后来经过若干个版本的迭代更新只有发现需要对Person类进行排序处理，但是又不能够去使用Comparable接口，所以这个时候就需要采用一种挽救的形式来实现比较。范例：实现自定义规则排序

1
package cn.cccc.demo;
2
import java.util.Arrays;
3
import java.util.Comparator;
4
public class Demo {
5
    public static void main(String[] args) {
6
       Person data [] = new Person [] {
7
               new Person("cc",20),
8
               new Person("ww",18)
9
       };
10
       Arrays.sort(data, new  PersonComparator());
11
       System.out.println(Arrays.toString(data));
12
    }
13
}
14
class Person{
15
    private String name;
27 collapsed lines
16
    private int age;
17
    public Person(String name , int age){
18
       this.name = name;
19
       this.age = age;
20
    }
21
    public String getName() {
22
       return name;
23
    }
24
    public void setName(String name) {
25
       this.name = name;
26
    }
27
    public int getAge() {
28
       return age;
29
    }
30
    public void setAge(int age) {
31
       this.age = age;
32
    }
33
    public String toString(){
34
       return "[个人信息]姓名"+this.name+"年龄："+this.age;
35
    }
36
}
37
class PersonComparator implements  Comparator<Person>{
38
    @Override
39
    public int compare(Person o1, Person o2)  {
40
       return o1.getAge() -o2.getAge();
41
    }
42
}