Java中的ConcurrentLinkedDeque removeLastOccurrence()方法

java.util.concurrent.ConcurrentLinkedDeque.removeLastOccurrence() 方法是Java中的一种内置方法，该方法接受一个参数并删除deque中该元素的最后一次出现。因此，如果deque中不存在该元素，则不会改变deque。

语法：

public boolean removeLastOccurrence(Object o)

参数： 函数接受一个对象作为参数，该对象表示要从deque中删除其最后一次出现的对象。

返回值： 如果deque中存在 elem ，则函数返回 true ，否则返回 false 。

异常： 如果将传递给函数的指定元素为空，则该函数会抛出 NullPointerException 异常。下面的程序演示了 removeLastOccurrence() 方法的用法：

/* Java program to demonstrate
   removeLastOccurrence() method
   of ConcurrentLinkedDeque   */
 
import java.util.concurrent.*;
 
class ConcurrentLinkedDequeDemo {
    public static void main(String[] args)
    {
        ConcurrentLinkedDeque<String> cld = new ConcurrentLinkedDeque<String>();
 
        cld.addFirst("GFG");
        cld.addFirst("Geeks");
        cld.addFirst("Gfg");
        cld.addFirst("gfg");
        cld.addFirst("Geeks");
 
        // Displaying the existing LinkedDeque
        System.out.println("Elements in "
                           + "the LinkedDeque: " + cld);
 
        // Remove last occurrence of  element
        cld.removeLastOccurrence("Geeks");
 
        // Displaying the modified LinkedDeque
        System.out.println("Elements in "
                           + "the LinkedDeque: " + cld);
    }
}

输出：

Elements in the LinkedDeque: [Geeks, gfg, Gfg, Geeks, GFG]
Elements in the LinkedDeque: [Geeks, gfg, Gfg, GFG]

程序2：

/* Java program to demonstrate
   removeLastOccurrence() 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(280);
        cld.addFirst(1008);
        cld.addFirst(1050);
        cld.addFirst(379);
 
        // Displaying the existing LinkedDeque
        System.out.println("Elements in "
                           + "the LinkedDeque: " + cld);
        try {
            // Remove last occurrence of  element
            cld.removeLastOccurrence(null);
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出：

Elements in the LinkedDeque: [379, 1050, 1008, 280, 12]
java.lang.NullPointerException

参考： https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentLinkedDeque.html#removeLastOccurrence()