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，根據年齡大的先出優先順序

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的優先佇列是小根堆(堆頂的元素為最小元素)，是根據自然排序來進行優先順序的判斷，所以自定義的類想要加進優先佇列中必須先實現Comparable介面，編寫compareTo的方法，方可以使用！