Java中的 ConcurrentLinkedDeque offerLast() 方法

Java.util.concurrent.ConcurrentLinkedDeque.offerLast() 方法是Java中的一个内置方法，它将作为参数传递的指定元素插入到双端队列的末尾。

句法：

Conn_Linked_Deque.offerLast(Object elem)

参数：该方法接受一个参数elem ，该参数指定要插入到双端队列末尾的元素。

返回值：如果元素成功添加到双端队列中，该函数返回True ，否则返回False 。

异常：如果传递的参数为NULL ，该函数将抛出NullPointerException 。

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

程序 1 ：

/* Java Program to Demonstrate offerLast()
   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("Elements in Deque: "
                           + cld);
  
        // Displaying the Last element
        System.out.println("The Last element is: " + 
                                      cld.getLast());
  
        /* Insert an element at the tail
            of the deque */
        if (cld.offerLast("GFG")) {
            // Displaying the Last element
            System.out.println("The Inserted element is: " + 
                                              cld.getLast());
        }
  
        // Displaying the Deque
        System.out.println("Elements in Deque: "
                           + cld);
  
        // Displaying the Last element
        System.out.println("The Last element is: " + 
                                      cld.getLast());
    }
}

输出：

Elements in Deque: [Welcome, To, Geeks, 4, Geeks]
The Last element is: Geeks
The Inserted element is: GFG
Elements in Deque: [Welcome, To, Geeks, 4, Geeks, GFG]
The Last element is: GFG

方案二：

/* Java Program to Demonstrate offerLast()
   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(12);
        cld.add(43);
        cld.add(29);
        cld.add(16);
        cld.add(70);
  
        // Displaying the Deque
        System.out.println("Elements in Deque: "
                           + cld);
  
        // Displaying the Last element
        System.out.println("The Last element is: " + 
                                      cld.getLast());
  
        try {
            cld.offerLast(null);
        }
        catch (Exception e) {
            System.out.println(e);
        }
  
        /* Insert an element at the tail
            of the deque */
        if (cld.offerLast(24)) {
            // Displaying the Last element
            System.out.println("The Inserted element is: "
                                          + cld.getLast());
        }
  
        // Displaying the Deque
        System.out.println("Elements in Deque: "
                           + cld);
  
        // Displaying the Last element
        System.out.println("The Last element is: " +
                                       cld.getLast());
    }
}

输出：

Elements in Deque: [12, 43, 29, 16, 70]
The Last element is: 70
java.lang.NullPointerException
The Inserted element is: 24
Elements in Deque: [12, 43, 29, 16, 70, 24]
The Last element is: 24

参考： https: Java/util/concurrent/ConcurrentLinkedDeque.html#offerLast()