• peek() 返回 null / 第一个元素

• poll() 返回 null / 第一个元素 并删除

• add(e) 加入元素

  public class PriorityQueueTest {

   public static void main(String[] args) {
       Queue<Integer> queue1 = new PriorityQueue<Integer>();
       queue1.add(2);
       queue1.add(1);
       queue1.add(3);
  
       while (!queue1.isEmpty()) {
           Integer i = queue1.poll();
           System.out.println(i);
       }
  
       Comparator<Student> comparator = new Comparator<Student>() {
           @Override
           public int compare(Student o1, Student o2) {
               return (o1.id - o2.id);
           }
       };
  
       Queue<Student> queue2 = new PriorityQueue<Student>(comparator);
       queue2.add(new Student(2, "B"));
       queue2.add(new Student(1, "A"));
       queue2.add(new Student(3, "C"));
  
       while (!queue2.isEmpty()) {
           Student s = queue2.poll();
           System.out.println(s.toString());
       }
   }
  
   public static class Student {
       private int id;
       private String name;
  
       public Student(int id, String name) {
           this.id = id;
           this.name = name;
       }
  
       public String toString() {
           return id + "-" + name;
       }
   }
  

  }

输出

1
2
3
1-A
2-B
3-C