java.lang Class NullPointerException

于 2009-07-13 10:13:56 发布 · 169 阅读

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本文详细介绍了Java中的NullPointerException，这是一种运行时异常，当应用程序试图在需要对象的地方使用null时抛出。例如，对null对象调用实例方法、访问或修改null对象的字段等场景。文章还解释了应用程序应如何通过抛出此类异常来指示对null对象的非法使用。

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java.lang
Class NullPointerException

java.lang.Object


  java.lang.Throwable


      java.lang.Exception


          java.lang.RuntimeException


              java.lang.NullPointerException

All Implemented Interfaces:

Serializable

public class NullPointerException

extends RuntimeException

Thrown when an application attempts to use null in a case where an object is required. These include:

Calling the instance method of a null object.
Accessing or modifying the field of a null object.
Taking the length of null as if it were an array.
Accessing or modifying the slots of null as if it were an array.
Throwing null as if it were a Throwable value.

Applications should throw instances of this class to indicate other illegal uses of the null object.