java - 声明 LinkedBlockingQueue 时出现 NullPointer 异常

Question

这是我的代码。我在构造函数的最后一行遇到空指针异常(workerQueue[i] = new LinkedBlockingQueue(100);):

public class QueueThreadPool {

  private BlockingQueue<String>[] workerQueue;
  private Thread[] workerThreads;
  private int numQueues;
  private int numThreads;

public QueueThreadPool(int numThreads, int numQueues) {
    this.numQueues = numQueues;
    this.numThreads = numThreads;

    for(int i=1; i<=numQueues; i++){
        workerQueue[i] = new LinkedBlockingQueue<String>(100);
    }
}
public static void main(String args[]){
    System.out.println("Start...");
    new QueueThreadPool(50, 11);
    System.out.println("End...");
}

请帮忙!谢谢!!

Answer 1

数组 workerQueue没有实例化您需要执行的操作。

private BlockingQueue<String>[] workerQueue;

workerQueue是 BlockingQueue<String>[] 的引用类型，而不是对象。

但是您也无法创建 BlockingQueue<String> 的通用数组。相反，创建一个 List的BlockingQueue<String> 。前-

private List<BlockingQueue<String>> workerQueue= new ArrayList<>();

您还可以在构造函数中创建列表对象。

private List<BlockingQueue<String>> workerQueue= new ArrayList<>();
public QueueThreadPool(int numThreads, int numQueues) {
    this.workerQueue = new ArrayList<>(numQueues);  // <-- initialize the field.
    this.numQueues = numQueues;
    this.numThreads = numThreads;
    ...