Question

Here is the method

public void addModuleToStudent(Module aModule)
 {
    int position = 0; 
    if(position > 3)
    {
        System.out.println("Error: Student already has four modules\n");
    }
    else
    {
        moduleArray[position] = aModule;
        position++;
    }
 }

The problem is that the position doesn’t seem to be increment the position variable because when ever I add a module class it occupies the 1st position in the the array and when I add another instead of being added into the second position it overwrites the first.

Answer 1

Yes, position is a local variable. Every time you call addModuleToStudent, you get a new variable, initialized as 0.

It sounds like you want to make this an instance variable instead, so that it persists between method calls.

Better yet, don’t use an array instead – use an ArrayList<Module> instead, and then you can just use:

public void addModuleToStudent(Module module)
{
    if (modules.size() > 3)
    {
        throw new SomeAppropriateException("Cannot have more than 4 modules");
    }
    modules.add(module);
}