// A Seq
//
// The Seq stores a sequence of objects
//
// We can: - add an object to the end of the sequence
//         - ask for the i^{th} object in the sequence
//         - ask for the length of the sequence
//         - insert an object inside the sequence
//         - delete an object from inside the sequence


import java.util.*;


interface Seq {

    public void   append( Object o );
    public Object elementAt( int pos );
    public int    getLength();
    public void   insert( int pos, Object o );
    public void   delete( int pos );
}


// Usually the interface and implementation would be in
// different files, but not in this example.


public class mySeqWithIterator implements Seq {

    private Object [] data;     // array to store objects
    private int capacity;       // size of array
    private int length;         // number of stored objects

    // Constructors

    mySeqWithIterator( int initialCapacity ) {
        length = 0;
        capacity = initialCapacity;
        data = new Object[ initialCapacity ];
    }

    mySeqWithIterator() {       // default Seq has capacity 10
        this( 10 );
    }


    // Iterator class

    private class mySeqIterator implements Iterator {

        private int nextIndex;

        mySeqIterator()
        {
            nextIndex = 0;
        }

        public boolean hasNext()
        {
            return (nextIndex < length);
        }

        public Object next()
            throws NoSuchElementException
        {
            if (nextIndex >= length)
                throw new NoSuchElementException();

            Object obj = data[ nextIndex ];
            nextIndex++;
            return obj;
        }

        public void remove()
            throws UnsupportedOperationException, IllegalStateException
        {
            throw new UnsupportedOperationException();
        }
    }

    public mySeqIterator createIterator() {
        return new mySeqIterator();
    }


    // Return the length of the sequence

    public int getLength() {
        return length;
    }


    // Append an object to the end of the sequence

    public void append( Object o ) {

        if (length == capacity) {

            // Double the size of the array

            Object [] newData = new Object[ capacity + 100 ];

            for (int j=0; j<capacity; j++)
                newData[j] = data[j];

            data = newData;
            capacity = capacity + 100;
        }

        // Store the object at the end of the sequence

        data[ length ] = o;
        length++;
    }


    // Return the object at a particular position in the sequence (base 0)

    public Object elementAt( int pos ) {

        // Test for out of bounds (should *really* throw an Exception)

        if (pos < 0 || pos > length) {
            System.out.println( "Seq::elementAt: position " + pos +
                                " is outside the range [0," + (length-1) + "]" );
            System.exit(1);
        }

        // Get the object

        return data[pos];
    }

    // Insert an Object at a particular position

    public void insert( int pos, Object o ) {}

    // Delete an Object at a particular position

    public void delete( int pos ) {}

    public static void main( String [] args ) {

        Random rand = new Random(1231432);
        mySeqWithIterator s = new mySeqWithIterator();

        // Fill up the Seq
 
        System.out.println( "Filling up:" );
        for (int i=0; i<10; i++) {
            int x = rand.nextInt(100);
            s.append( new Integer(x) );
            System.out.print( " " + x );
        }
        System.out.println( "" );

        // Iterate over the Seq

        Iterator iter = s.createIterator();

        System.out.println( "Iterating over:" );
        while (iter.hasNext())
            System.out.print( " " + iter.next().toString() );
        System.out.println( "" );
    }
}