Why is this throwing a null pointer exception?

Question

I have the following piece of code inside a for loop

MyClass myobj= new MyClass(customers, price);
System.out.println(myobj);
if (!myobj.equals(null)) { //same happesn with myobj != null
    System.out.println("not null");
}
myMethod(myobj);

myMethod body is:

private void myMethod(MyClass myobj) {
   if (myobj.totalDemand()) {
      //bla bla
   }

After running the code in Junit the line "if (myobj.totalDemand())" throws a NullPointerException, however the console prints "not null"

Answer 1

If you call myobj.equals(null) , there's no guarantee that the implementation of equals() for the class will not throw a NullPointerException , and if myobj is null , you'll get a NullPointerException trying to invoke .equals() on a null object.

To test for null , use this code:

if (myobj == null)

and to test for not null, use this:

if (myobj != null)

Answer 2

If myobj is null you will get NullPointerException, and if it's not console will print out "not null". So, is there anything in variables customers and price in EVERY invoke cycle ?