Common places where Java NullPointerException usually occur
- 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
Full Answer
How to handle NullPointerException in Java?
How does Java handle NullPointerException for integers?
- Check Each Object For Null Before Using.
- Check Method Arguments for Null.
- Consider Primitives Rather than Objects.
- Carefully Consider Chained Method Calls.
- Make NullPointerExceptions More Informative.
Why do I get a null pointer exception?
- 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?
Null Pointer Exception mostly occurs because of the null object or null reference. We have already seen the causes and ways to avoid NullPointerException. As far as possible, the programmer should try to avoid the occurrence of Null Pointer Exception in a program. As this is an unchecked runtime exception, we should see that it doesn’t occur ...
How to check if object is null in Java?
Avoiding Null Checks Through Coding Practices
- 6.1. Preconditions. It's usually a good practice to write code that fails early. ...
- 6.2. Using Primitives Instead of Wrapper Classes. Since null is not an acceptable value for primitives like int, we should prefer them over their wrapper counterparts like Integer wherever possible.
- 6.3. Empty Collections. ...
How do you fix a 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 causes NullPointerException in Java?
What Causes NullPointerException. The NullPointerException occurs due to a situation in application code where an uninitialized object is attempted to be accessed or modified. Essentially, this means the object reference does not point anywhere and has a null value.
How do I fix NullPointerException processing?
1 AnswerMake sure your image files have been added to your sketch. They should be inside a data directory inside your sketch folder. Make sure they're spelled correctly.Make sure you're calling the loadImage() function before trying to call the image() function.
How do I get around 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. Use valueOf() instead of toString() ; and both return the same result.
How do I stop NullPointerException?
To avoid the NullPointerException, we must ensure that all the objects are initialized properly, before you use them. When we declare a reference variable, we must verify that object is not null, before we request a method or a field from the objects.
Which of the following will help us to avoid NullPointerException in Java 8?
Java 8 introduced an Optional class which is a nicer way to avoid NullPointerExceptions. 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.
How do you handle exceptions in Java?
The try-catch is the simplest method of handling exceptions. Put the code you want to run in the try block, and any Java exceptions that the code throws are caught by one or more catch blocks. This method will catch any type of Java exceptions that get thrown. This is the simplest mechanism for handling exceptions.
What is null in Java?
Null keyword Null is a reserved keyword in the Java programming language. It's technically an object literal similar to True or False. Null is case sensitive, like any other keyword in Java.
How do you check if an object is null?
Typically, you'll check for null using the triple equality operator ( === or !== ), also known as the strict equality operator, to be sure that the value in question is definitely not null: object !== null . That code checks that the variable object does not have the value null .
How do you handle a null check in Java?
10 Tips to Handle Null EffectivelyDon't Overcomplicate Things. ... Use Objects Methods as Stream Predicates. ... Never Pass Null as an Argument. ... Validate Public API Arguments. ... Return Empty Collections Instead of Null. ... Optional Ain't for Fields. ... Use Exceptions Over Nulls. ... Test Your Code.More items...•
How do you return a null object in Java?
In Java, a null value can be assigned to an object reference of any type to indicate that it points to nothing. The compiler assigns null to any uninitialized static and instance members of reference type. In the absence of a constructor, the getArticles() and getName() methods will return a null reference.
What does nullpointer exception mean?
You are not checking any of the result values. So, if one of those calls returns "null" and you try to subsequently use it as if it were a reference/pointer to an object, that's where your NullPointerException comes from.
Can System Console return null?
It has to be System.console (). You are not doing any other operation on an object that would cause a null pointer exception. And as @McDowell has pointed out, System.console () can return a null value
