Java中Comparable和Comparator实现对象比较

当需要排序的集合或数组不是单纯的数字型时，通常可以使用Comparator或Comparable，以简单的方式实现对象排序或自定义排序。下面通过两个例子分别用Comparable和Comparator实现对User对象中年龄排序。

1.通过实现Comparable接口，根据User的年龄进行排序。

import java.util.Arrays;

/**
 * @author pengcqu
 * 
 */
public class ComparableUser implements Comparable {

    private String id;
    private int age;

    public ComparableUser(String id, int age) {
        this.id = id;
        this.age = age;
    }

    public int getAge() {
        return age;
    }

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

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public int compareTo(Object o) {
        return this.age - ((ComparableUser) o).getAge();
    }

    /**
     * 测试方法
     */
    public static void main(String[] args) {
        ComparableUser[] users = new ComparableUser[] {
                new ComparableUser("u1001", 25),
                new ComparableUser("u1002", 20),
                new ComparableUser("u1003", 21) };
        Arrays.sort(users);
        for (int i = 0; i < users.length; i++) {
            ComparableUser user = users[i];
            System.out.println(user.getId() + " " + user.getAge());
        }
    }

}

2. 通过实现Comparator接口，根据User的年龄进行排序。

public class User {

    private String id;
    private int age;

    public User(String id, int age) {
        this.id = id;
        this.age = age;
    }

    public int getAge() {
        return age;
    }

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

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }
    

}

import java.util.Arrays;
import java.util.Comparator;

/**
 * @author pengcqu
 * 
 */
public class UserComparator implements Comparator {

    public int compare(Object arg0, Object arg1) {
        return ((User) arg0).getAge() - ((User) arg1).getAge();
    }

    /**
     * 测试方法
     */
    public static void main(String[] args) {
        User[] users = new User[] { new User("u1001", 25),
                new User("u1002", 20), new User("u1003", 21) };
        Arrays.sort(users, new UserComparator());
        for (int i = 0; i < users.length; i++) {
            User user = users[i];
            System.out.println(user.getId() + " " + user.getAge());
        }
    }
}