Java ConcurrentLinkedDeque addFirst()用法及代码示例

java.util.concurrent.ConcurrentLinkedDeque.addFirst()是Java中的内置函数，它将指定的元素插入ConcurrentLinkedDeque的前面。

用法:

conn_linked_deque.addFirst(elem)

参数：该方法仅接受要添加到ConcurrentLinkedDeque开头的单个参数elem。

返回值：该函数没有返回值。

异常：当传递给函数的参数为null时，该方法将引发NullPointerException。由于其有限的性质，此方法将永远不会引发IllegalStateException或返回false。

以下示例程序旨在说明ConcurrentLinkedDeque.addFirst()方法：

示例1:该程序涉及一个Integer类型的ConcurrentLinkedDeque。

// Java Program Demonstrate addFirst() 
// method of ConcurrentLinkedDeque  
  
import java.util.concurrent.*; 
  
class ConcurrentLinkedDequeDemo { 
    public static void main(String[] args) 
    { 
        ConcurrentLinkedDeque<Integer> cld =  
                     new ConcurrentLinkedDeque<Integer>(); 
  
        cld.addFirst(12); 
        cld.addFirst(110); 
        cld.addFirst(55); 
        cld.addFirst(76); 
  
        // Displaying the existing LinkedDeque 
        System.out.println("Initial Elements in"
                           + "the LinkedDeque: " + cld); 
  
        // Insert a new element in the  LinkedDeque 
        cld.addFirst(21); 
  
        // Displaying the modified LinkedDeque 
        System.out.println("Initial Elements in"
                           + "the LinkedDeque: " + cld); 
    } 
}

输出：

Initial Elements inthe LinkedDeque: [76, 55, 110, 12]
Initial Elements inthe LinkedDeque: [21, 76, 55, 110, 12]

示例2:当将null作为参数传递给函数时，此程序涉及一个带有异常处理的Integer类型的ConcurrentLinkedDeque。

// Java Program Demonstrate addFirst() 
// method of ConcurrentLinkedDeque  
  
import java.util.concurrent.*; 
  
class ConcurrentLinkedDequeDemo { 
    public static void main(String[] args) 
    { 
        ConcurrentLinkedDeque<String> cld =  
                         new ConcurrentLinkedDeque<String>(); 
  
        cld.addFirst("Geeks"); 
        cld.addFirst("Geek"); 
        cld.addFirst("Gfg"); 
        cld.addFirst("Contribute"); 
  
        // Displaying the existing LinkedDeque 
        System.out.println("Initial Elements in"
                           + "the LinkedDeque: " + cld); 
  
        /* Exception thrown when null  
             is passed as parameter*/
        try { 
            cld.addFirst(null); 
        } 
        catch (NullPointerException e) { 
            System.out.println("NullPointerException"
                               + "thrown"); 
        } 
  
        // Insert a new element in the  LinkedDeque 
        cld.addFirst("Sudo Placement"); 
  
        // Displaying the modified LinkedDeque 
        System.out.println("Initial Elements in"
                           + "the LinkedDeque: " + cld); 
    } 
}

输出：

Initial Elements inthe LinkedDeque: [Contribute, Gfg, Geek, Geeks]
NullPointerExceptionthrown
Initial Elements inthe LinkedDeque: [Sudo Placement, Contribute, Gfg, Geek, Geeks]

参考： https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentLinkedDeque.html#addFirst()

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注：本文由纯净天空筛选整理自RICHIK BHATTACHARJEE大神的英文原创作品 ConcurrentLinkedDeque addFirst() method in Java。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。