Java排序之集合排序

集合排序

• 要么让集合的对象具有比较性也就是让集合中的对象实现Comparable<T>接口
• 自定义比较器实现Comparator<T>

举例：按人的年龄排序

代码如下

• UserBean对象

/**
 * Created by yuandl on 2016-10-10.
 */
public class UserBean implements Comparable<UserBean> {
    private String name;
    private int age;

    public UserBean(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "UserBean{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    @Override
    public int compareTo(UserBean o) {
        return this.age-o.age;
    }
}

• 主要代码

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

/**
 * Created by yuandl on 2016-10-10.
 */
public class ListTest {
    public static void main(String args[]) {
        List<UserBean> list = new ArrayList<>();
        list.add(new UserBean("张三", 56));
        list.add(new UserBean("张2", 5));
        list.add(new UserBean("张6", 34));
        list.add(new UserBean("张5", 6));
        list.add(new UserBean("张9", 76));
        Collections.sort(list);//让list中的对象具有比较性即UserBean implements Comparable<UserBean>
        Collections.sort(list, new Comparator<UserBean>() {//自定义比较器
            @Override
            public int compare(UserBean o1, UserBean o2) {
                return o1.getAge()-o2.getAge();
            }
        });
        System.out.println(list);
    }
}