Null pointer exception

If you operate on NULL, a null pointer exception is generated
Object obj = new Object ();
You know, obj is an object pointer variable that points to an instance of the object class

If this pointer variable obj does not point to any space, the method and the property you call it will go wrong.
For example, object obj = new Object ();
     Obj.equals ("123"); this one's right.
But change the following statement to Object obj = null;
     Obj.equals ("123"); Null pointer exception appears


Your object is not instantiated!
In other words, null values
Let's take an example:
There's a student class.
Student objstudent = null;
Then you use objstudent directly to invoke the method in the student class.
Conversely, if you add objstudent = new Student () between the two sentences;
Then there's no problem!

Null pointer exception