Java BlockingDeque removeFirstOccurrence()方法及示例

BlockingDeque 的 removeFirstOccurrence() 方法会从这个deque中删除第一次出现的指定元素。如果该deque不包含该元素，它将保持不变。如果这个deque包含指定的元素，则返回true，否则返回false。

语法

public boolean removeFirstOccurrence(Object o)

参数： 该方法接受一个强制性参数 o ，它指定了要从Deque容器中删除的元素。

返回： 如果该元素存在并从Deque容器中删除，该方法返回 true ，否则返回 false

注意 ： BlockingDeque 的 removeFirstOccurrence() 方法继承自Java中的LinkedBlockingDeque类。

以下程序说明了BlockingDeque的removeFirstOccurrence()方法。

程序1： 当元素存在时

// 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<Integer> BD
            = new LinkedBlockingDeque<Integer>();
 
        // 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 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<Integer> BD
            = new LinkedBlockingDeque<Integer>();
 
        // 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]

参考资料： https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/BlockingDeque.html#removeFirstOccurrence(java.lang.Object)