Java中的 BlockingDeque removeFirstOccurrence() 方法及示例

BlockingDeque的removeFirstOccurrence()方法从这个双端队列中删除指定元素的第一个匹配项。如果双端队列不包含该元素，则它保持不变。如果此双端队列包含指定的元素，则返回 true，否则返回 false。

句法：

public boolean removeFirstOccurrence(Object o)

参数：此方法接受一个强制参数o ，它指定要从 Deque 容器中删除的元素。

返回：如果元素存在并从 Deque 容器中删除，则此方法返回true ，否则返回false 。

注意： BlockingDeque的removeFirstOccurrence()方法继承自Java中的 LinkedBlockingDeque 类。
下面的程序说明了 BlockingDeque 的 removeFirstOccurrence() 方法：

程序 1：当元素存在时

Java

// Java Program to demonstrate removeFirstOccurrence()
// 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)
        throws InterruptedException
    {
 
        // create object of BlockingDeque
        BlockingDeque BD
            = new LinkedBlockingDeque();
 
        // Add numbers to end of BlockingDeque
        BD.add(15);
        BD.add(20);
        BD.add(20);
        BD.add(15);
 
        // print Deque
        System.out.println("Blocking Deque: " + BD);
 
        if (BD.removeFirstOccurrence(15))
            System.out.println("First occurrence of 15 removed");
        else
            System.out.println("15 not present and not removed");
 
        // prints the Deque after removal
        System.out.println("Blocking Deque: " + BD);
    }
}

输出

Blocking Deque: [15, 20, 20, 15]
First occurrence of 15 removed
Blocking Deque: [20, 20, 15]

程序 2：当元素不存在时

Java

// Java Program to demonstrate removeFirstOccurrence()
// 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)
        throws InterruptedException
    {
 
        // create object of BlockingDeque
        BlockingDeque BD
            = new LinkedBlockingDeque();
 
        // Add numbers to end of BlockingDeque
        BD.add(15);
        BD.add(20);
        BD.add(20);
        BD.add(15);
 
        // print Deque
        System.out.println("Blocking Deque: " + BD);
 
        if (BD.removeFirstOccurrence(10))
            System.out.println("First occurrence of 10 removed");
        else
            System.out.println("10 not present and not removed");
 
        // prints the Deque after removal
        System.out.println("Blocking Deque: " + BD);
    }
}

输出：

Blocking Deque: [15, 20, 20, 15]
10 not present and not removed
Blocking Deque: [15, 20, 20, 15]

参考： https: Java Java.lang.Object)