Question

I recall seeing, somewhere, an example that stepped through String args[] by deleting the lowest numbered value(s)

public static void main( String args[]) {
    while (args.length > 0 ) {
    // do something and obliterate elements from args[]
    }
}

Obviously, a variable tracking current position in args and compared to args.length will do it; or an ArrayList made from args[]’s contents, with argsAL.size(). Am I mis-remembering an ArrayList example? I know this is a borderline question, the likely answer is, “No, there isn’t and there shouldn’t be either!”. Maybe I’m over-focused…

Bill

Answer 1

No, there isn’t and there shouldn’t be either! Deleting from the front of an array would be a needlessly expensive way to do this.

You might be thinking of many scripting languages having a shift operator to dequeue the next element (perl, bash, etc).

Edit: Just for posterity, here’s a pretty simple implementation of Queue that would allow you to “fake” the same functionality (i.e. encapsulate the cursor):

class ArrayQueue<E> extends AbstractQueue<E> {

    private int cursor = 0;
    private final E[] data;

    public ArrayQueue(E[] data) {
        this.data = data;
    }

    private boolean inRange() {
        return cursor < data.length;
    }

    @Override
    public E peek() {
        return inRange() ? data[cursor] : null;
    }

    @Override
    public E poll() {
        return inRange() ? data[cursor++] : null;
    }

    @Override
    public boolean offer(E e) {
        throw new UnsupportedOperationException();
    }

    @Override
    public void clear() {
        cursor = data.length;
    }

    @Override
    public Iterator<E> iterator() {
        //ommitted for brevity
    }

    @Override
    public int size() {
        return data.length - cursor;
    }

}

Usage:

public static void main(String[] args) throws Exception {
    Queue<String> argQ = new ArrayQueue<String>(args);
    String command = argQ.poll();
    String target = argQ.poll();
}

Warning: Untested