Question

这个代码正常，我的意思是多线程部分.. 唯一的问题是，只有当我调用保存方法

时才能获得 NPE

线程中的异常＆＃34; pool-1-thread-1＆＃34;显示java.lang.NullPointerException 在app.Controller.handleClient（Controller.java:54）在app.Controller.run（Controller.java:109） at java.util.concurrent.ThreadPoolExecutor.runWorker（Unknown Source） at java.util.concurrent.ThreadPoolExecutor $ Worker.run（Unknown Source）在java.lang.Thread.run（未知来源）

我该如何处理？谢谢

编码部分

BlockingQueue<Client> clients_list;

ExecutorService executor = Executors.newFixedThreadPool(10);

for (Client client: clients_list) {
        Runnable worker = new Controller(client);
        executor.execute(worker);
}

public Controller(Client client) {
        this.client = client;
}

// Controller类实现了Runnable，这里是run方法 @覆盖 public void run（）{ //在客户端上做一些事情 //然后将数据保存到文件中 handleClient（客户端）; }

private void handleClient(Client client) {
    String c_rwx = client.getPermission()
    if(c_rwx.contains("allowed to:")) {
       client.setUsername = client.getUsername() + " allowed" ;
       save(client);
    }
}

private void save(Client client) {
        FileWriter fw = null;
        try {
            File file = new File("done.txt");
            if (!file.exists()) {
                file.createNewFile();
            }
            fw = new FileWriter(file, true);
            fw.write("client info:" + client.getUsername() + " \n");
            // ...
            fw.flush();
        } catch (IOException ex) {
            System.out.println("err saving file");
        }
}

固定一切在for

之后添加

executor.shutdown();

多线程空指针异常java

0 个答案: