Java PriorityQueue poll() 方法

2024 年 11 月 9 日 | 阅读 2 分钟

PriorityQueue 类的 poll() 方法会检索此队列的头部，并将其移除。如果此队列为空，则该方法返回 null。

语法

参数

不适用

返回值

poll() 方法返回此队列的头部，如果此队列为空，则返回 null。

示例 1

import java.util.PriorityQueue;

public class PriorityQueuePollExample1 {
	public static void main(String[] args) {
PriorityQueue<String>Pqueue = new PriorityQueue<String>();
Pqueue.add("Ramesh");
Pqueue.add("Yasir");
Pqueue.add("Mark");
Pqueue.add("Robert");

        String val = Pqueue.poll();

System.out.println("Head of queue is: "+val);
System.out.println("Queue after using poll() method : ");
for(String xyz : Pqueue)
        {
	System.out.println(xyz);
        }   
    }
}

输出

Head of queue is: Mark
Queue after using poll() method : 
Ramesh
Robert
Yasir

示例 2

import java.util.Comparator;
import java.util.PriorityQueue;
import java.util.Queue;

class Student {
int marks;
    String name;
public Student(int marks, String name) {
this.marks= marks;
this.name = name;
    }
public String toString(){
return this.name+" got "+ this.marks+" marks.";
    }
}
class sort implements Comparator<Student>{

@Override
public int compare(Student s1, Student s2) {
if(s1.marks<s2.marks)
return 1;
else if(s1.marks>s2.marks)
return -1;
return 0;
    }
}
public class PriorityQueuePollExample2 {
public static void main(String[] args) {
        Student student1 = new Student(77,"Hinna");
        Student student2 = new Student(87,"Vinni");
        Student student3 = new Student(97,"Rima");
        Queue<Student> queue = new PriorityQueue<Student>(1,new sort());
queue.add(student1);
queue.add(student2);
queue.add(student3);
System.out.println(queue.poll().name+" stood First in the class");
System.out.println(queue.poll().name+" stood Second in the class");
System.out.println(queue.poll().name+" stood Third in the class");
    }
}

输出

Rima stood First in the class
Vinni stood Second in the class
Hinna stood Third in the class

示例 3

import java.util.PriorityQueue;

class Patient implements Comparable{
    String name;

public Patient(String name) {
this.name = name;
    }
@Override
public int compareTo(Object o) {
return 0;
    }
}
public class PriorityQueuePollExample3 {
public static void main(String[] args) {
PriorityQueue<Patient>Pqueue = new PriorityQueue<Patient>();
        Patient p1 = new Patient("Arnavi");
        Patient p2 = new Patient("Himani");
        Patient p3 = new Patient("Sarita");
Pqueue.add(p1);
Pqueue.add(p2);
Pqueue.add(p3);
System.out.println(Pqueue.poll().name+" can visit the doctor at first. ");
System.out.println(Pqueue.poll().name+" can visit the doctor after the first patient. ");
System.out.println(Pqueue.poll().name+" can visit the doctor after the second patient. ");
    }
}

输出

Arnavi can visit the doctor at first. 
Sarita can visit the doctor after the first patient. 
Himani can visit the doctor after the second patient.

下一主题Java-priorityqueue-remove-method

Java PriorityQueue poll() 方法

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示例 1

示例 2

示例 3

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Java PriorityQueue poll() 方法

语法

参数

返回值

示例 1

示例 2

示例 3

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