How do I fix null pointer exception in Java?

How do I fix null pointer exception 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 type of error is a null pointer exception in Java?

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.

How do you handle a null pointer exception in a list in Java?

Effective Java NullPointerException Handling

1. Check Each Object For Null Before Using.
2. Check Method Arguments for Null.
3. Consider Primitives Rather than Objects.
4. Carefully Consider Chained Method Calls.
5. Make NullPointerExceptions More Informative.

What are null pointer exceptions?

A null pointer exception is thrown when an application attempts to use null in a case where an object is required. These include: Calling the instance method of a null object. Accessing or modifying the field of a null object.

Can we catch null pointer exception?

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.

How do I stop null dereference in Java?

There are some coding conventions we can use to avoid NullPointerException . Use methods that already guard against null values, such as String#equals , String#valueOf , and third party libraries that help us check whether string or collection is empty.

How do you handle null values 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.

Can null pointer exception be caught?

It is generally a bad practice to catch NullPointerException. Programmers typically catch NullPointerException under three circumstances: The program contains a null pointer dereference. Catching the resulting exception was easier than fixing the underlying problem.

When is a null pointer exception thrown in Java?

Null Pointer Exception In Java. 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. These can be: Invoking a method from a null object. Accessing or modifying a null object’s field.

Which is the default value for null in Java?

Null is the default value in Java assigned to the variables which are not initialized by the user after or with a declaration. Consider the following example where you declare a variable like this: And then try to print the contents of the variable: As can be seen above, ‘null’ gets printed on the output.

What happens if STR reference is null in Java?

The message variable will be empty if str’s reference is null as in case 1. Otherwise, if str point to actual data, the message will retrieve the first 6 characters of it as in case 2. This article is contributed by Nikhil Meherwal.

Which is an example of an application of null?

One application of null is in implementing data structures like linked list and tree. Other applications include Null Object pattern (See this for details) and Singleton pattern. The Singleton pattern ensures that only one instance of a class is created and also, aims for providing a global point of access to the object.