What is NullPointerException Mcq?
Answer: null pointer exception is a run time exception and it is thrown when the program attempts to use an object reference that has null value. For example, calling a method or variable using an object which has null value or say object reference is null will cause run time exception.
What do you understand by null pointer?
A null pointer has a reserved value that is called a null pointer constant for indicating that the pointer does not point to any valid object or function. You can use null pointers in the following cases: Initialize pointers. Represent conditions such as the end of a list of unknown length.
What causes NullPointerException?
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. Accessing or modifying an instance field of the object referred by a null reference.
What is null check in Java?
In Java, null is a literal. It is mainly used to assign a null value to a variable. A null value is possible for a string, object, or date and time, etc. We cannot assign a null value to the primitive data types such as int, float, etc.
Where are null pointer points?
A null pointer is a pointer pointing to the 0th memory location, which is a reserved memory and cannot be dereferenced. In the above code, we create a pointer *ptr and assigns a NULL value to the pointer, which means that it does not point any variable.
Why is null better than Optional?
In a nutshell, the Optional class includes methods to explicitly deal with the cases where a value is present or absent. However, the advantage compared to null references is that the Optional class forces you to think about the case when the value is not present.
Why am I getting a NullPointerException in Java?
If you run this code as is, you will get the following exception: Exception in thread “main” java.lang.NullPointerException The reason you are getting this error is because we are trying to perform the length () operation on str1 which is null. An easy fix for this is to add a null check on str1 as shown below:
Why am I getting NullPointerException in the statement t foo?
We are getting NullPointerException in the statement t.foo (“Hi”); because “t” is null here. 2. Java NullPointerException while accessing/modifying field of a null object
What happens if the null check is not present in Java?
If the null check is not present, then trying to loop over a null list will throw a NullPointerException. Let’s take the scenario where you need to access the value for a particular key in a map:
What can you do with a null object in Java?
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. Throwing null, as if it were a Throwable value.