PriorityBlockingQueue的peek()方法返回PriorityBlockingQueue开头的元素。它检索LinkedBlockingQueue头的值,但不删除它。如果PriorityBlockingQueue不包含任何元素,则此方法返回null。 PriorityBlockingQueue队列使用与类PriorityQueue相同的排序规则。
用法:
public E peek()
参数:此方法不带任何参数。
返回值:此方法返回PriorityBlockingQueue的头部。
下面的程序说明PriorityBlockingQueue的peek()方法。
示例1:
// Java Program Demonstrate peek()
// method of PriorityBlockingQueue
import java.util.concurrent.PriorityBlockingQueue;
public class GFG {
public static void main(String[] args)
{
// define capacity of PriorityBlockingQueue
int capacityOfQueue = 5;
// create object of PriorityBlockingQueue
PriorityBlockingQueue<Integer> PrioQueue
= new PriorityBlockingQueue<Integer>(capacityOfQueue);
// Add elements to PriorityBlockingQueue
PrioQueue.add(464161);
PrioQueue.add(416165);
// print PrioQueue
System.out.println("PrioQueue: " + PrioQueue);
// get head of PriorityBlockingQueue
int head = PrioQueue.peek();
// print head of PriorityBlockingQueue
System.out.println("Head of Queue: " + head);
}
}
输出:
PrioQueue: [416165, 464161] Head of Queue: 416165
示例2:为了说明PriorityBlockingQueue的peek()方法,该方法包含名称列表。
// Java Program Demonstrate peek()
// method of PriorityBlockingQueue
import java.util.concurrent.PriorityBlockingQueue;
public class GFG {
public static void main(String[] args)
{
// define capacity of PriorityBlockingQueue
int capacityOfQueue = 5;
// create object of PriorityBlockingQueue
PriorityBlockingQueue<String> names
= new PriorityBlockingQueue<String>(capacityOfQueue);
// Add names of students of girls college
names.add("Geeks");
names.add("forGeeks");
names.add("A");
names.add("Computer");
names.add("Portal");
// print PrioQueue
System.out.println("List of Names: " + names.toString());
// get head of PriorityBlockingQueue
String head = names.peek();
// print head of PriorityBlockingQueue
System.out.println("Head of Queue: " + head);
// remove one name from head
names.poll();
System.out.println("First Name from head is removed");
// print PrioQueue
System.out.println("List of Names: " + names.toString());
// get head of PriorityBlockingQueue
head = names.peek();
// print head of PriorityBlockingQueue
System.out.println("Head of Queue: " + head);
}
}
输出:
List of Names: [A, Computer, Geeks, forGeeks, Portal] Head of Queue: A First Name from head is removed List of Names: [Computer, Portal, Geeks, forGeeks] Head of Queue: Computer
参考:
https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/PriorityBlockingQueue.html#peek–
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注:本文由纯净天空筛选整理自AmanSingh2210大神的英文原创作品 PriorityBlockingQueue peek() method in Java。非经特殊声明,原始代码版权归原作者所有,本译文未经允许或授权,请勿转载或复制。