null pointer exception

Programming Questions

stackofpo..

in Programming Questions • 2 years ago

I'm getting a null pointer exception for this bit of code:

class Menubar

{

private Menu[] Menus;

private int numMenus=0;

//Creates an empty menubar

Menubar() {}

void addMenu (String name)

{

Menus[numMenus]=new Menu(name);

numMenus++;

}

and then this line in draw:

menubar.addMenu("File");

What am I doing wrong? Do I need to declare the size of the Menu array? Is there a way around that?

Replies(4)

Psysoul

Re: null pointer exception

2 years ago

Yes, you should declare the size, maybe in the constructor. (but If I remember right: without it you get something like variable not initialized error...).

You can use ArrayList, then you don't need to define the size.

niteshade

Re: null pointer exception

2 years ago

Yeah, you need a line like this:

private Menu[] Menus = new Menu[25];

where 25 is the number of menubars you think you might need.

Psysoul is right... ArrayLists are a lot more flexible for arrays which can change size at runtime. But if you don't need to change at runtime, Arrays are just fine, and a bit easier to use (in my experience). ArrayLists are flexible, but a little slower, and a little more complicated.

stackofpo..

Re: null pointer exception

2 years ago

I'm still getting a null pointer exception with:

private Menu[] Menus=new Menu[25];

PhiLho

Re: null pointer exception

2 years ago

You have to do a menubar = new Menubar() too... Before using it.

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