Java 中的 BlockingDeque peek()方法，带示例
原文:https://www . geeksforgeeks . org/blocking eque-peek-method-in-Java-with-examples/
阻塞请求的 peek() 方法返回德格容器中的前元素。如果容器是空的，它将返回空值。
语法:
public E peek()
参数:此方法不接受任何参数。
返回:如果容器不是空的，该方法返回德清容器中的前元素。如果容器为空，则返回 false。
注:blocking eque的 peek()方法继承自 Java 中的link edblocking eque类。
下面的程序说明了 peek()方法的阻塞请求:
程序 1:
// Java Program Demonstrate peek()
// method of BlockingDeque
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.BlockingDeque;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// create object of BlockingDeque
BlockingDeque<Integer> BD
= new LinkedBlockingDeque<Integer>();
// Add numbers to end of BlockingDeque
BD.add(7855642);
BD.add(35658786);
BD.add(5278367);
BD.add(74381793);
// Print the queue
System.out.println("Linked Blocking Deque: " + BD);
System.out.println("Front element in Deque: " + BD.peek());
}
}
输出:
Linked Blocking Deque: [7855642, 35658786, 5278367, 74381793]
Front element in Deque: 7855642
程序二:
// Java Program Demonstrate peek()
// method of BlockingDeque
// when Deque is empty
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.BlockingDeque;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// create object of BlockingDeque
BlockingDeque<Integer> BD
= new LinkedBlockingDeque<Integer>();
// Add numbers to end of BlockingDeque
BD.add(7855642);
BD.add(35658786);
BD.add(5278367);
BD.add(74381793);
// Print the queue
System.out.println("Blocking Deque: " + BD);
// empty deque
BD.clear();
System.out.println("Front element in Deque: " + BD.peek());
}
}
输出:
Blocking Deque: [7855642, 35658786, 5278367, 74381793]
Front element in Deque: null
参考:https://docs . Oracle . com/javase/7/docs/API/Java/util/concurrent/blockingdequee . html # peek()
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