(And if you do need to model that, then your application has to cope with this possibility. It is as simple as it is.U have no option to write them together in single constructor body.

The first alternative is probably the correct one, unless you really need to model the possibility that an 'attendee' has purchased an unknown number of tickets. According to Java this () and super () should be the first statement in constructor.Now the point is we can not write both at once as a first line.If u write this () and not super,dont expect that super will be called implicitly. and propagate the change to the places where the corresponding field value is returned, used, etcetera.

Change the type of the formal parameter from int to Integer. When a constructor is declared without any parameter or argument, then it is called a parameter-less constructor. In this case, zero looks like a reasonable substitute. Pass an int value, or an actual (not null) Integer object. In this case, zero looks like a reasonable substitute.Ĭhange the type of the formal parameter from int to Integer. Possible solutions: Dont use (Integer) null as the parameter. However, this is legal Java code, so a conformant Java compiler cannot call this a compilation error.ĭon't use (Integer) null as the parameter. There cannot be any return statement in the constructor. There cannot be any return type in the constructor definition. The constructor name MUST be the same as the name of the class.

Let’s see the specification of the constructor: Throws Clause . There are a few mandatory rules for creating the constructors in Java.

Its structure looks similar to a method, but it has different purposes. Some compilers will issue a warning for this, saying that the code will always throw an NPE. In Java, every class must have a constructor. not a real object reference.Īt runtime, you end up calling intValue() on the null, and that throws an NPE. The code to unbox the value is a call to Integer.intValue(), using the value-to-be-unboxed as the target object.

The Java compiler is going to say 'Ah! I have an Integer value, and I need to convert it to an int value. When the formal type of a method argument is int and you try to pass (Integer) null, the following is going to happen. As other answers mention, the problem is this - (Integer) null.

This java constructor