"No Such Element Exception" Error.

Error Manifestation: “NullPointerException” error in java is seen when an uninitialized object is accessed.

Understand the Error: “NullPointerException” is a common runtime error in Java that occurs when an application attempts to use a null object reference, which means that the object does not point to any memory location.

Causes:

·       Not initializing an object reference

·       Assigning a null value to an object variable

·       Accessing an element of a null array

·       Trying to call a method on a null object reference

·       Accessing a non-static field or method from a static content

Check: Can you check where this error is occurring in your code? (Exact file name and line no.)

Check: Check if any of the above causes is applicable to your code. Why do you think the error is being thrown on this line?

Debugging the error:

Debug 1: Uninitialized object reference.

1.     Check for the object that is declared but not initialized.

2.     Try to initialize some values to the object while declaring.

Debug 2: Check if you are accessing an object that has been initialized as ‘null’.

Debug 3: Accessing an element of a null array.

1.     Check for an array that has been initialized as ‘null’.

2.     Check for an uninitialized array.

Debug 4: Calling a method on a null object reference.

1.     Do not call a method on a null object reference.

Debug 5: Accessing a non-static field or method from a static content

1.     All the fields or methods not having a ‘static’ keyword before the fields or methods name are referred to as ‘Non-Static fields/methods’.

2.     Add the ‘static’ keyword before the fields or methods name.

3.     Another method to remove this error is by creating an object of the class to refer to a non-static variable from a static context.

Code Snippets for reference:

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