Javascript Null Pointer Exception

Michael Zippo 04.11.2021

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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.

Example of Java. lang.NullPointer.Exception

Finding examples of java.lang.NullPointerException is not a difficult task, as all you need to do is not initialize a variable before trying to access it. For example, consider the StringBuilder class. StringBuilder is a class used to handle the formation and manipulation of strings. Here’s how the class would normally be used to create strings:

If you run the above snippet, it will work fine. Let’s look at the modified version which will throw a null pointer exception:

As you can see, we haven’t initialized an instance of the StringBuilder class as we stated. When the sb.append () lines are executed, sb does not point to any object, it points to null. This is where a NullPointerException is thrown. Due to the thrown exception, the JVM cannot execute any instructions after this.

How to fix the java.lang.NullPointerException error

Creating a null pointer exception is easy, but avoiding or fixing it is tricky. While some integrated development environments (IDEs) warn you if you access a variable before initializing it with a compatible value, most IDEs cannot understand this in complex situations, such as when you pass a variable through multiple method calls. The exact fix for a null pointer exception depends on the situation and the code. Here are some of the best ways to fix common null pointer scenarios:

Check your code for manual errors

The main reason that null pointer exceptions occur is human error. Make sure the program you wrote has the correct logic you initially expected. Also check the source code to see if you missed any instructions or misspelled any variables that might prevent you from assigning a value to a variable.

Make sure you wrote your code as your logic tells you and that you haven’t missed write instructions or have incorrectly referenced objects. is initialized with an object.

Perform security checks around the code that may cause a null pointer exception

If you know the line of code that is causing your NullPointer and think your logic is correct too, you can wrap the section of code in a try-catch block and define the behavior when a null pointer is caught. looks like:

This happens occurs in situations where a certain reference variable may or may not contain null. Most of the time, remote API responses and device interface responses are subject to this scenario. Depending on the availability of a result or a material, the response variable may or may not point to an instantiated object. The use of security controls is best suited to handle these situations.

Check for null before accessing anything

This method is similar to the try-catch method. In this method, an ’if’ block is used to check for null values ‚Äã‚Äãbefore accessing a variable. Here’s what the above code snippet would look like if an " if " block is used to catch the error:

The biggest difference between the two methods is the scope of the checks they perform . The if method checks the myVar variable for null values ‚Äã‚Äãonly, while the try-catch block captures all null variables.

This makes the ’if’ block a more focused and cleaner approach to inserting null pointers into application logic. However, if there are multiple variables that can be null, it is better to use a try-catch block for simplicity.

Conclusion

This article examined what the Null Pointer exception is in Java and how this error occurs. We also looked at a piece of code that will cause a null pointer exception to understand how null pointers are created in real life situations.Finally, we decided to identify some of the best ways to fix a null pointer exception and we have finished our discussion comparing two methods of correcting NPEs.

If you are trying to write Java programs, one Null Pointer exception is one of the essential bugs that you should know how to fix. This exception is one of the most common problems and is unrelated to the syntax or semantics of the code. This makes the exception one of the most difficult problems to identify and solve. A quick reference to resolve this issue as this article is intended to make your experience smoother.

We hope this article has helped you to resolve the problem. Apart from Javascript Null Pointer Exception, check other __main__ Python module-related topics.