What is null pointer exception in Java example?

What is a NullPointerException in Java?

NullPointerException is a runtime exception in Java that occurs when a variable is accessed which is not pointing to any object and refers to nothing or null. Since the NullPointerException is a runtime exception, it doesn’t need to be caught and handled explicitly in application code.

How do I fix NullPointerException in Java?

In Java, the java. lang. NullPointerException is thrown when a reference variable is accessed (or de-referenced) and is not pointing to any object. This error can be resolved by using a try-catch block or an if-else condition to check if a reference variable is null before dereferencing it.

What is a NullPointerException give an example?

NullPointerException is a runtime exception and it is thrown when the application try to use an object reference which has a null value. For example, using a method on a null reference.

Why do we use NullPointerException in Java?

NullPointerException is thrown when program attempts to use an object reference that has the null value. … Accessing or modifying the slots of null object, as if it were an array. Throwing null, as if it were a Throwable value. When you try to synchronize over a null object.

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Is NullPointerException checked or unchecked?

Answer: NullPointerException is not a checked exception. It is a descendant of RuntimeException and is unchecked.

What is an exception in coding?

Definition: An exception is an event, which occurs during the execution of a program, that disrupts the normal flow of the program’s instructions. When an error occurs within a method, the method creates an object and hands it off to the runtime system. … This block of code is called an exception handler.

Can we catch NullPointerException?

As stated already within another answer it is not recommended to catch a NullPointerException. However you definitely could catch it, like the following example shows. Although a NPE can be caught you definitely shouldn’t do that but fix the initial issue, which is the Check_Circular method.

Can we catch NullPointerException in Java?

Java NullPointerException is an unchecked exception and extends RuntimeException . NullPointerException doesn’t force us to use catch block to handle it. This exception is very much like a nightmare for most of java developer community. They usually pop up when we least expect them.

What is checked exception?

A checked exception is a type of exception that must be either caught or declared in the method in which it is thrown. For example, the java.io.IOException is a checked exception.

What is null in Java?

In Java, null is a reserved word for literal values. It seems like a keyword, but actually, it is a literal similar to true and false.

Why am I getting null in Java?

In Java, a special null value can be assigned to an object reference. NullPointerException is thrown when an application attempts to use an object reference that has the null value. These include: Calling an instance method on the object referred by a null reference.

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How do you check if an object is null?

There are 3 different ways to do a null check:

  1. Object.ReferenceEquals(obj, null) ReferenceEquals returns true when the object instances are the same instance. …
  2. object.Equals(obj, null) Equals is similar to ReferenceEquals when one argument is null . …
  3. obj == null.

How do you handle null in Java?

10 Tips to Handle Null Effectively

  1. Don’t Overcomplicate Things. …
  2. Use Objects Methods as Stream Predicates. …
  3. Never Pass Null as an Argument. …
  4. Validate Public API Arguments. …
  5. Leverage Optional. …
  6. Return Empty Collections Instead of Null. …
  7. Optional Ain’t for Fields. …
  8. Use Exceptions Over Nulls.

What is checked and unchecked exception?

1) Checked: are the exceptions that are checked at compile time. If some code within a method throws a checked exception, then the method must either handle the exception or it must specify the exception using throws keyword. … 2) Unchecked are the exceptions that are not checked at compiled time.

Is Filenotfoundexception a runtime exception?

I know FileNotFound is Checked Exception but though it is, only during the Run time this exception will occur.It is more like Arithmetic Exception(Unchecked). Whether it is checked or unchecked the exception will happen only during runtime.