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You must have encountered something called NullPointerException if you have worked on Java based applications. One of the most common errors in developing Java applications is the null pointer exception. This exception is usually the result of human error, but time can be wasted debugging errors like this. This problem is not entirely a syntax error, so it can sometimes be difficult to identify it.
In this article, let’s take a look at what java.lang.NullPointerException is, why it occurs, how you can fix it, and some of the best practices to avoid hitting wild null pointers . Without further ado, let’s get started.
What is java.lang.NullPointerException ?
The Null Pointer exception is one of the many exceptions supported by the Java language. This indicates that an attempt was made to access a reference variable that currently points to null.
Null is the default value in Java assigned to variables that are not initialized by the user after or with an instruction. Consider the following example where you declare a variable like this:
And then try to print the contents of the variable:
As you can see above, ’null’ is printed on the output. This shows that since the variable str is not initialized, it currently points to, or holds the value, null. The problem with a zero pointing variable is that the variable is only a reference and does not point to anything. If you try to perform certain operations on the data stored in a zero-pointing variable, the system will not know what to do. This happens because there is no data actually stored in the variable; points to an empty entity.