java.lang.Thread.run(Thread.java:745)
<p>When i use cycle sentence to run two Threads it shows me that problem:java.lang.Thread.run(Thread.java:745) 
but i figure it out use two methods:\
first if i dont run the application just debug it and use breakpoint it would be ok . 
second based on my demo just has two threads so i could copy this part of code "</p>

<pre><code>    new Thread(new Runnable() {
                    @Override
                    public void run() {
                        int data = new Random().nextInt();
                        System.out.println(Thread.currentThread().getName()
                                + " has put data:" + data);
                        threadDataMap.put(Thread.currentThread(), data);
                        new A().get();
                        new B().get();
                    }
                }).start();

"
</code></pre>

<p>for twice it would also be ok .</p>

<p>all my demo code is below:</p>

<pre><code>    package 多线程;

    import java.util.HashMap;
    import java.util.Map;
    import java.util.Random;

    public class ThreadScopShareData {

    private static int data = 0;
    private static Map&lt;Thread,Integer&gt; threadDataMap=new HashMap&lt;Thread,Integer&gt;();
    public static void main(String[] args) {
        for (int i = 0; i &lt; 2; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    int data = new Random().nextInt();
                    System.out.println(Thread.currentThread().getName()
                            + " has put data:" + data);
                    threadDataMap.put(Thread.currentThread(), data);
                    new A().get();
                    new B().get();
                }
            }).start();
        }
    }

    static class A {
        public void get() {
            int data=threadDataMap.get(Thread.currentThread());
            System.out.println("A from " + Thread.currentThread().getName()
                    + "get data:" + data);
        }
    }

    static class B {
        public void get() {
            int data=threadDataMap.get(Thread.currentThread());
            System.out.println("B from " + Thread.currentThread().getName()
                    + "get data:" + data);
        }
    }
    }
</code></pre>

<p>and the right result should be like below:
    Thread-1 has put data :-1188249922
    Thread-0 has put data :1024718434
    A from Thread-0 get data :1024718434
    B from Thread-0 get data :1024718434
    A from Thread-1 get data :-1188249922
    B from Thread-1 get data :-1188249922</p>

<p>but the bug is below:Thread-1 has put data :-807205084
   Thread-0 has put data :-976943511
   A from Thread-0 get data :-976943511</p>

<pre><code>   Exception in thread "Thread-1" B from Thread-0 get data :-976943511
    java.lang.NullPointerException
    at 多线程.ThreadScopeShareData$A.get(ThreadScopeShareData.java:33)
    at 多线程.ThreadScopeShareData$1.run(ThreadScopeShareData.java:22)
    at java.lang.Thread.run(Thread.java:745)
</code></pre>

<p>As far as i know the Thread-1 would totally change and kill the thread-0 so it would appear a nullPointerException . but i am not sure.</p>