What causes a NullPointerException?

NullPointerException is a RuntimeException. In Java, a special null value can be assigned to an object reference. 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.

How do you stop NullPointerException in Java?

Answer: Some of the best practices to avoid NullPointerException are:

1. Use equals() and equalsIgnoreCase() method with String literal instead of using it on the unknown object that can be null.
2. Use valueOf() instead of toString() ; and both return the same result.
3. Use Java annotation @NotNull and @Nullable.

What is Java Lang NullPointerException error?

The java. lang. NullPointerException is an error in Java that occurs as a Java program attempts to use a null when an object is required. Similarly, if an object is null and you try to access or modify the field of that null object, this error will occur.

What is null in Java?

In Java, null is a reserved word (keyword) for literal values. It seems like a keyword, but actually, it is a literal similar to true and false. The reserved word null is case sensitive and we cannot write null as Null or NULL, the compiler will not recognize them and give an error.

What do you understand by null pointer?

A null pointer is a pointer which points nothing. Some uses of the null pointer are: a) To initialize a pointer variable when that pointer variable isn’t assigned any valid memory address yet. b) To pass a null pointer to a function argument when we don’t want to pass any valid memory address.

What is null and 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 you check if an object is null?

To check if it is null, we call the isNull() method and pass the object getUserObject as a parameter. It returns true as the passed object is null.

IS null == null in Java?

if(obj. equals(null)) // Which mean null. equals(null) when obj will be null. When your obj will be null it will throw Null Point Exception.

Why do I get a null pointer exception?

I can list out some more reasons of NullPointerException from here: Invoking methods on an object which is not initialized Parameters passed in a method are null Calling toString () method on object which is null Comparing object properties in if block without checking null equality Incorrect configuration for frameworks like spring which works on dependency injection Using synchronized on an object which is null

Why do I get a NullPointerException?

Calling the instance method of a null object.

What is arithmetic exception in Java?

Arithmetic Exception is a kind of unchecked error in Java and these kind of exception occurs, when you divide a number by zero or if there is a mathematical or calculation errors that occurs at the RunTime. java.lang.ArithmeticException is the base class of arithmetic exceptions that extends Runtime Exception.

What is Io exception in Java?

Java IO Exception Handling From Java 7. From Java 7 on and forward Java contains a new exception handling mechanism called “try with resources”. This exception handling mechanism is especially targeted at handling exception handling when you are using resources that need to be closed properly after use, like InputStream, OutputStream etc.