Java中的 ConcurrentLinkedDeque contains() 方法及示例

Java.util.concurrent.ConcurrentLinkedDeque.contains() 方法是Java中的一个内置方法，它检查作为参数传递的指定元素是否存在于双端队列中。

句法：

public boolean contains(Object elem)

参数：该方法接受一个参数elem ，它检查指定的元素是否存在于双端队列中。

返回值：如果元素存在于双端队列中，该函数返回True ，否则返回False 。

下面的程序说明了ConcurrentLinkedDeque.contains()方法：

程序 1 ：

// Java Program to Demonstrate contains()
// method of ConcurrentLinkedDeque
  
import java.util.concurrent.*;
  
class GFG {
    public static void main(String[] args)
    {
  
        // Creating an empty Deque
        ConcurrentLinkedDeque cld = new ConcurrentLinkedDeque();
  
        // Add elements into the Deque
        cld.add("Welcome");
        cld.add("To");
        cld.add("Geeks");
        cld.add("4");
        cld.add("Geeks");
  
        // Displaying the Deque
        System.out.println("ConcurrentLinkedDeque: "
                           + cld);
  
        // Check if GFG is present using contains()
        if (cld.contains("GFG")) {
  
            // Displaying message
            System.out.println("GFG is present");
        }
        else {
  
            // Displaying message
            System.out.println("GFG is not present");
        }
    }
}

输出：

ConcurrentLinkedDeque: [Welcome, To, Geeks, 4, Geeks]
GFG is not present

方案二：

// Java Program to Demonstrate contains()
// method of ConcurrentLinkedDeque
  
import java.util.concurrent.*;
  
class GFG {
    public static void main(String[] args)
    {
  
        // Creating an empty Deque
        ConcurrentLinkedDeque cld = new ConcurrentLinkedDeque();
  
        // Add elements into the Deque
        cld.add("Welcome");
        cld.add("To");
        cld.add("Geeks");
        cld.add("4");
        cld.add("Geeks");
  
        // Displaying the Deque
        System.out.println("ConcurrentLinkedDeque: "
                           + cld);
  
        // Check if Geeks is present using contains()
        if (cld.contains("Geeks")) {
  
            // Displaying message
            System.out.println("Geeks is present");
        }
        else {
  
            // Displaying message
            System.out.println("Geeks not present");
        }
    }
}

输出：

ConcurrentLinkedDeque: [Welcome, To, Geeks, 4, Geeks]
Geeks is present

参考： https://docs.oracle.com/javase/9/docs/api/ Java/util/concurrent/ConcurrentLinkedDeque.html#contains-java.lang.Object-