Question

If I have a 2d array of objects, and want to initialize them all, I call a loop, eg:

for(int i=0; i<len; i++)
    for(int j=0; j<len; j++)
        objects[i][j] = new MyObject();

Which works fine, but when I tried doing this with the for-each construct, it didn’t work and the entire array remains null:

for(MyObject[] intermediate: objects)
    for(MyObject obj: intermediate)
        obj = new MyObject();

How come they behave differently?

Answer 1

The assigment

obj = new MyObject();

just set a new object in the variable obj, and does not change the value in the array, it only changes the reference variable obj.

What happens is that objects[i][j] is assined to obj, and then you change the value of obj, without changing the actual array.

when you assign directly to objects[i][j] – it works as expected, since you change the value of objects[i][j], which is exactly what you want to do.