Comparable和Compartor的区别

1.List对象实现Comparable接口，使对象具备可比性

package tao;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class Student1 implements Comparable<Student1> {
    private String name;
    private Integer age;
    public Student1(String name, Integer age) {
        super();
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    @Override
    public int compareTo(Student1 o) {
        // TODO Auto-generated method stub
        return this.getAge().compareTo(o.getAge());
    }

    // 测试方法
    public static void main(String[] args) {
        List<Student1> list = new ArrayList<Student1>();

        Student1 s1 = new Student1("lisi1",);
        Student1 s2 = new Student1("lisi3",);
        Student1 s3 = new Student1("lisi2",);

        list.add(s1);
        list.add(s2);
        list.add(s3);

        Collections.sort(list);

        for(Student1 s : list){
            System.out.println("name:"+s.getName()+" age:"+s.getAge());
        }
    }
}

排序结果
name:lisi3 age:
name:lisi1 age:
name:lisi2 age:

2.List对象不具备可比性，或者对象本身可比性不是想要的排序规则，通过Comparator外部比较

package tao;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class Student2 {
    private String name;
    private Integer age;
    public Student2(String name, Integer age) {
        super();
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }

    // 测试方法
    public static void main(String[] args) {
        List<Student2> list = new ArrayList<Student2>();

        Student2 s1 = new Student2("lisi1",);
        Student2 s2 = new Student2("lisi3",);
        Student2 s3 = new Student2("lisi2",);

        list.add(s1);
        list.add(s2);
        list.add(s3);

        Collections.sort(list,new MyCompare());

        for(Student2 s : list){
            System.out.println("name:"+s.getName()+" age:"+s.getAge());
        }
    }
}

class MyCompare implements Comparator<Object> {

    @Override
    public int compare(Object o1, Object o2) {
        // TODO Auto-generated method stub
        Student2 s1 = (Student2)o1;
        Student2 s2 = (Student2)o2;
        return s1.getAge().compareTo(s2.getAge());
    }
}

排序结果
name:lisi3 age:
name:lisi1 age:
name:lisi2 age:

3.Comparable和Compartor的区别

a.出处不同

java.util.Comparator;

java.lang.Comparable;

 b.提供方法不同

Comparator提供int compare(Object o1, Object o2)

Comparable提供int compareTo(Object o)

 c.内外部区别

Comparator提供外部对比

Comparable提供对象自身对比