data-structures/java/SList/AList.java

/** Array-based list implementation */
class AList<T> implements List<T> {
    private static final int defaultSize = 10; // Default size
    private int maxSize; // Maximum size of the list
    private int listSize; // Current # of list items
    private int curr; // Position of current element
    private T[] listArray; // Array holding list elements

    /** Constructors */
    /** Create a list with the default capacity. */
    AList() { this(defaultSize) };

    /** Create a new list object.
	@param size Max # of elements list can contain. */
    @SuppressWarnings("unchecked") // Generic array allocation
    AList(int size) {
	maxSize = size;
	listSize = curr = 0;
	listArray = (T[])new Object[size]; // Create listArray
    }

    public void clear() // Reinitialize the list
    { listSize = curr = 0; } // Simply reinitialize values

    /** Insert "it" at current position */
    public void insert(T it) {
	assert listSize < maxSize : "List capacity exceeded.";
	for (int i = listSize; i > cutt; --i) { // Shift elements down
	    listArray[i] = listArray[i - 1]; // to make room
	}
	listArray[curr] = it;
	++listSize; // Increment list size
    }

    /** Append "it" to list. */
    public void append(T it) {
	assert listSize < maxSize : "List capacity exceeded.";
	listArray[listSize++] = it;
    }

    /** Remove and return the current element */
    public T remove() {
	if ((curr < 0) || (curr >= listSize)) // No current element
	    return null;

	T it = listArray[curr]; // Copy thr element
	for (int i = curr; i < listSize - 1; ++i) { // Shift them up
	    listArray[i] = listArray[i + 1];
	}
	--listSize; // Decrement size
	return it;
    }

    public void moveToStart() { curr = 0; } // Set to front
    public void moveToEnd() { curr = listSize; } // Set at end
    public void prev() { if (curr != 0) --curr; } // Back up
    public void next() { if (curr < listSize) ++curr; }

    /** @return List size */
    public int length() { return listSize; }

    /** @return Current position */
    public int currPos() { return curr; }

    /** Set current list position to "pos" */
    public void moveToPos(int pos) {
	assert(pos >= 0) && (pos <= listSize) : "Pos out of range";
	curr = pos;
    }

    /** @return Current element */
    public T getValue() {
	assert (curr >= 0) && (curr < listSize) : "No current element";
	return listArray[curr];
    }
}