Array List help please

[keo]

I need help with another Array, I've created a miniature version of my code, and the same error is there. It compiles fine in Bluej.

A contains an array, C is the Array object. B is to create a new C and add it to A.

Problem:
- B: call addToArrayInA(1, "string")
- then get Null error in the same method, 2nd line.

 myC.add(newC);

What do I do here, if I go A.add(newC); it will cause non static variable error...

import java.util.ArrayList;
public class A
{
       ArrayList<C> c;

    /**
     * Constructor for objects of class A
     */
    public A()
    {
        c = new ArrayList<C>();
    }

    public void add(C neww) {
        c.add(neww);
    }
    public C get(int i) {
        C get = c.get(i);
        return get;
    }
}

public class B
{
    private A myC;

    public B()
    {
        
    }

    public void addToArrayInA(int one, String two) {
        C newC = new C(one, two);
        A.add(newC);
    }
    
    public C getC() {
        int i = 0;
        C cc = myC.get(i);
        return cc;
    }
}

public class C
{
    private int o;
    private String t;
    public C(int one, String two)
    {
        o = one;
        t = two;
    }
    
}

[pbrockway2]

You call myC.add(newC) but myC is of type C, not A.

Perhaps you mean

private A myA;
// initialise myA somewhere not shown

public void addToArray(int one, String two) {
    C newC =new C(one, two);
    myA.add(newC);
}

public C getC() {
    return cc = myA.get(0)
}

If not, then code that's minimal but enough to illustrate the problem and actually runnable would be good.

[keo]

I've edited my original post...

[pbrockway2]

It shouldn't be "A.add(newC)", but "myC.add(newC)". See my earlier post (where I called the variable myA) and note the comment there about how myA will have to be initialised somewhere.

[Edit]

I've just reread the OP. That null pointer exception you are seeing is because you haven't initialised myC somewhere. You can do that either in the line where you declare it, or in the B constructor.

[keo]

I tried changing it, but am still not sure what to do, can you edit that code in the first post, So I can compare it with my code please?

EDIT: Oh I understand what is wrong now. but How would I initialize an empty one because its already an arraylist?

    private A myC;

    public B()
    {
        myC = new ArrayList<C>(10); //initialise with 10 slots?
        myC = ...??
    }

Thank you!

Edit. Figured it out! its myC = new C;

[pbrockway2]

Something like that should do. But note: myC is of type A not C.