Inserting values into the array

[gnawk]

Hi im trying to insert a value into the array and expand it when the array gets full

	public void insert(Comparable T) {
		if (full()) {
			Comparable[] tempArray = new Comparable[size + increment];
			for (int i = 0; i < size; i++) {
				tempArray[i] = array[i];
				array = tempArray;
			}
			for (int j = 0; j < top; j++) {
				j = appropriatePosition(j);
				array[j] = T;
			}
		} else if (!full()) {
			for (int j = 0; j < top; j++) {
				j = appropriatePosition(T);
				array[j] = T;
			}
		}
		
	}

	public int appropriatePosition(Comparable T) {
		int i = 0;
		while (i <= top) {
			if (array[i].compareTo(T) >= 0){
				count ++;
				return i;
			}
			else
				i = i + 1;
		}
		return top + 1;
	}

when i run the program it won't insert anything into the array and shows all null
my initial size of the array is 5 and it should increment by 5 when the array is full
since top is not declared i added
top = array[size - 1] but it gives me nullpointer exception and i don't know what to do

[awinston]

This looks a bit off:

 for (int i = 0; i < size; i++) {
            tempArray[i] = array[i];
            array = tempArray;
        }

Shouldn't moving the array located in the variable tempArray to the variable array be done after the for-loop?

[JosAH]

You're about to reinvent the wheel; it has been done in the ArrayList class.

kind regards,

Jos

[gnawk]

my professor wants us to know how to program it from the scratch so he won't let us use arraylist

[Tolls]

awinston has identified your problem, but this:

else if (!full())

should just be an 'else'. Save you doing whatever full() does twice. At this point you know that full() is false.

[gnawk]

finally fixed the problem with inserting......
time to move on to deleting the element from the array T.T