What does java.lang.nullpointerexception mean?

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. The NullPointerException is a public class that extends the RuntimeException. The NullPointerException is thrown for different scenarios, for example, if you call the instance method of an object which is null.
In this manner, what is a null reference exception?
A NullReferenceException exception is thrown when you try to access a member on a type whose value is null. A NullReferenceException exception typically reflects developer error and is thrown in the following scenarios: You've forgotten to instantiate a reference type.
Likewise, what are null interfaces in Java? A null interface is an interface without any methods.Is also known as Marker interface. Null interfaces are used to inform Java regarding what it can do with a class.
Also, when to use optional to avoid nullpointerexception?
You can use Optional to encapsulate the potential null values and pass or return it safely without worrying about the exception. Without Optional, when a method signature has return type of certain object. The user often tend to assert the existence of the object. Hence, the possibility of null is often ignored.
Moreover, when do you get a nullpointerexception in java?
According to the Javadoc for NullPointerException, it's thrown when an application attempts to use null in a case where an object is required, such as: Calling an instance method of a null object Accessing or modifying a field of a null object Taking the length of null as if it were an array

18 Similar Question Found

What does nullpointerexception do in java keymanagerfactory?

NullPointerException - if algorithm is null. Returns a KeyManagerFactory object that acts as a factory for key managers. A new KeyManagerFactory object encapsulating the KeyManagerFactorySpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.

When to use nullpointerexception in trust manager?

NoSuchAlgorithmException - if no Provider supports a TrustManagerFactorySpi implementation for the specified algorithm. NullPointerException - if algorithm is null. Returns a TrustManagerFactory object that acts as a factory for trust managers.

Why do i get nullpointerexception while pasting in bukkit?

While pasting, i keep getting a NullPointerException in the pasting process. When i logged what items were getting placed, i see grass blocks, stone, but not my chests, anything in the chests, or beacons (Maybe even more blocks).

What's the difference between isnullorempty and nullpointerexception?

Yes , the only difference is NullPointerException. In isNullOrEmpty first it will check string is null or not .if it is not null then it will check it is check string is empty or not . If any of the condition will true then method will return true.

When do you get a nullpointerexception in sslcontext?

NoSuchAlgorithmException - if no Provider supports a SSLContextSpi implementation for the specified protocol. NullPointerException - if protocol is null. Returns a SSLContext object that implements the specified secure socket protocol.

What does the nullpointerexception do in java?

NullPointerException in Java is a runtime exception. Java assigns a special null value to an object reference. When a program tries to use an object reference set to the null value, then this exception is thrown.

When to throw nullpointerexception back at the caller?

If the caller passes null, but null is not a valid argument for the method, then it's correct to throw the exception back at the caller because it's the caller's fault. Silently ignoring invalid input and doing nothing in the method is extremely poor advice because it hides the problem.

Is the nullpointerexception a checked or unchecked exception?

Answer: NullPointerException is not a checked exception. It is a descendant of RuntimeException and is unchecked. #3) How do I stop NullPointerException? Answer: Some of the best practices to avoid NullPointerException are: Use equals () and equalsIgnoreCase () method with String literal instead of using it on the unknown object that can be null.

Why does java.util.collections throw a nullpointerexception?

It contains polymorphic algorithms that operate on collections, "wrappers", which return a new collection backed by a specified collection. The methods of this class all throw a NullPointerException if the collections or class objects provided to them are null. Following is the declaration for java.util.Collections class −

Why did i get a nullpointerexception in mockito?

But definitely, NullPointerException happened because you want something which is not there. Check if you are returning something. 2. Specify Mockito running class

When do i get a nullpointerexception exception?

You might get NullPointerException exception when you try to mock object in your tests. This article is a short list of 3 most common reasons why this might be happening. Here is a working example of DocumentRepositoryTest class for reference: @RunWith (MockitoJUnitRunner.class) public final claNewDs DocumDTOoryTest { @Mock private ...

Why do i get nullpointerexception when mocking documentrepository?

DocumentRepositoryTest class is mocking documentRepository object. So you are running your test and suddenly you see NullPointerException: You looked it up, and it seems your test is written correctly. So what might be a problem if you know how the mocking works?

What causes the nullpointerexception to be thrown?

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. Taking the length of null, as if it were an array. Accessing or modifying the slots of null object, as if it were an array.

When to use catch block for nullpointerexception?

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. I have also spent a lot of precious time while looking for reasons and best approaches to handle such issues.

When does findfirst throw nullpointerexception in java?

If the selected element by findFirst is null, it throws NullPointerException . The findFirst method returns Optional containing first element in the stream. The findFirst throws NullPointerException if selects null value. The findFirst is a short-circuiting terminal operation.

Is there a nullpointerexception in mulesoft mule 4?

There was a NullPointerException while resolving metadata for an account that didn’t have a Change Data Capture event channel set. (CONN-8146) The Query Result Stream operation returned only the first set of results when reading the result of a batch query that contained multiple response IDs.

When to throw nullpointerexception in java stream?

The method argument shall be a non-interfering, stateless Comparator. The method returns an Optional describing the smallest element of this stream, or an empty Optional if the stream is empty. It may throw NullPointerException if the smallest element is null. 2. Java Stream min () Example

When to throw a nullpointerexception in webtarget?

NullPointerException - if path is null. Create a new WebTarget instance by resolving a URI template with a given name in the URI of the current target instance using a supplied value. In case a null template name or value is entered a NullPointerException is thrown.