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public class Instance
{

public static Instance instance = new Instance();

public static Map<String, String> map = new HashMap<String, String>();

public static Instance instance()
{

return Instance.instance;
}

public static void main(String[] args)
{
Instance.instance().test();
}
public Instance()
{
Instance.map.put("abc", "def");
}

public void test()
{

System.out.println("test called");
}
}

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java.lang.ExceptionInInitializerError
Caused by: java.lang.NullPointerException
 at edu.bupt.test.Instance.<init>(Instance.java:27)
 at edu.bupt.test.Instance.<clinit>(Instance.java:9)
Exception in thread "main"
µ±Ê±Ã»ÓÐ̫עÒâÕâ¸öException£¬ÒòΪ»¹ÓÐÁíÍâÒ»¸öNullException
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