通过一个实例讲解 Collections.sort() 用法

Collections.sort() 方法应该是开发中最常用的排序方法吧！

下面通过一个例子讲解简单用法：

// 首先定义一个 POJO
public class User {
    
    String name;
    
    String age;
    
    public User(String name, String age) {
        this.name = name;
        this.age = age;
    }
    
    public String getAge() {
        return age;
    }
    
    public void setAge(String age) {
        this.age = age;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
}

// 再定义 POJO 的比较类 
import java.util.Comparator;

public class UserComparator implements Comparator {
    
    public int compare(Object arg0, Object arg1) {
        User user0 = (User) arg0;
        User user1 = (User) arg1;
        // 首先比较年龄，如果年龄相同，则比较名字 
        int flag = user0.getAge().compareTo(user1.getAge());
        if (flag == 0) {
            return user0.getName().compareTo(user1.getName());
        } else {
            return flag;
        }
    }
}

// 测试方法 
public static void main(String[] args) {
    List userlist = new ArrayList();
    userlist.add(new User("dd", "4"));
    userlist.add(new User("aa", "1"));
    userlist.add(new User("ee", "5"));
    userlist.add(new User("bb", "2"));
    userlist.add(new User("ff", "5"));
    userlist.add(new User("cc", "3"));
    userlist.add(new User("gg", "6"));
    
    UserComparator comparator = new UserComparator();
    Collections.sort(userlist, comparator);
    
    for (int i = 0; i < userlist.size(); i++) {
        User user_temp = (User) userlist.get(i);
        System.out.println(user_temp.getAge() + "," + user_temp.getName());
    }
    
}

结果：