Java优先队列使用

1，根据年龄小的先出优先级

class Person implements Comparable<Person>{
    public int age;   
    Person(int age){
    this.age=age;
    }
    public int compareTo(Person other){
        
        return age-other.age;
    
    }
    
}
public class Main {

    public static void main (String[] args) {
        PriorityQueue<Person> q=new PriorityQueue<Person>();
        Person a=new Person(10);
         Person b=new Person(20);
        q.offer(a);
        q.offer(b);
        System.out.println(q.peek().age);
    }

}

2，根据年龄大的先出优先级

class Person implements Comparable<Person>{
    public int age;   
    Person(int age){
    this.age=age;
    }
    public int compareTo(Person other){
        
        return other.age-age;
    
    }
    
}
public class Main {

    public static void main (String[] args) {
        PriorityQueue<Person> q=new PriorityQueue<Person>();
        Person a=new Person(10);
         Person b=new Person(20);
        q.offer(a);
        q.offer(b);
        System.out.println(q.peek().age);
    }

}

Java的优先队列是小根堆(堆顶的元素为最小元素)，是根据自然排序来进行优先级的判断，所以自定义的类想要加进优先队列中必须先实现Comparable接口，编写compareTo的方法，方可以使用！