// An implementation of a rectangular vector.// (c) 1998, 2001 duane a. baileypackage structure;/** * An implementation of rectangular vectors. * This implementation of a Matrix is minimal.  Few operations * are provided, and no support for mathematical operations * is considered. * <P> * Example Usage: * <P> * <pre> * public static void main(String[] argv){ *	//create an array of arrays to bet copied into the matrix *	int[][] test = new int[][]{new int[]{1,2,3}, *				   new int[]{4,5,6},  *				   new int[]{7,8,9}}; * *	//create the matrix *	Matrix testMatrix = new {@link #Matrix(int, int) Matrix(test.length, test[0].length)}; *	 *	//copy the 2-d array into the matrix *	for(int i = 0; i < test.length; i++){ *	    for(int j = 0; j < test[0].length; j++){ *		testMatrix.{@link #set(int, int, Object) set(i,j,new Integer(test[i][j]))}; *	    } *	} * *	//print out the matrix *	System.out.println(testMatrix); *  } * </pre> * @version $Id: Matrix.java,v 4.1 2000/12/29 02:57:55 bailey Exp bailey $ * @author, 2001 duane a. bailey */public class Matrix{    protected int height, width; // size of matrix    protected Vector rows;       // vector of row vectors    /**     * Construct an empty matrix.     *     * @post constructs empty matrix<br>     *     */    public Matrix()    {	this(0,0);    }    /**     * Constructs a matrix such that all values are null.     *     * @pre h >= 0, w >= 0;<br>     * @post constructs an h row by w column matrix<br>     *     * @param h Height of the matrix.     * @param w Width of the matrix.     */    public Matrix(int h, int w)    {	height = h;  // initialize height and width	width = w;	// allocate a vector of rows	rows = new Vector(height);	for (int r = 0; r < height; r++)	{   // each row is allocated and filled with nulls	    Vector theRow = new Vector(width);	    rows.add(theRow);	    for (int c = 0; c < width; c++)	    {		theRow.add(null);	    }	}    }    /**     * Fetch an element from the matrix.     * @pre 0 <= row < height(), 0 <= col < width()<br>     * @post returns object at (row, col)<br>     *     * @param row The row of the element     * @param col The column of the element     * @return Object located at matrix position (row, col)     */    public Object get(int row, int col)    {	Assert.pre(0 <= row && row < height, "Row in bounds.");	Assert.pre(0 <= col && col < width, "Col in bounds.");	Vector theRow = (Vector)rows.get(row);	return theRow.get(col);    }    /**     * Change the value at location (row, col)     * @pre 0 <= row < height(), 0 <= col < width()<br>     * @post changes location (row, col) to value<br>     *     * @param value The new Object reference (possibly null).     * @param row The row of the value to be changed.     * @param col The column of the value to be changed.     */    public void set(int row, int col, Object value)    {	Assert.pre(0 <= row && row < height, "Row in bounds.");	Assert.pre(0 <= col && col < width, "Col in bounds.");	Vector theRow = (Vector)rows.get(row);	theRow.set(col,value);    }    /**     * Add a new row, whose index will be r.     *     * @pre 0 <= r < height()<br>     * @post inserts row of null values to be row r<br>     *     * @param r The index of the  newly inserted row.     */    public void addRow(int r)    {	Assert.pre(0 <= r && r < width, "Row in bounds.");	height++;	Vector theRow = new Vector(width);	for (int c = 0; c < width; c++)	{	    theRow.add(null);	}	rows.add(r,theRow);    }    /**     * Add a new column, whose index will be c.     *     * @pre 0 <= c < width()<br>     * @post inserts column of null values to be column c<br>     *     * @param c The index of the newly inserted column.     */    public void addCol(int c)    {	Assert.pre(0 <= c && c < width, "Col in bounds.");	width++;	for (int r = 0; r < height; r++)	{	    Vector theRow = (Vector)rows.get(r);	    theRow.add(c,null);	}    }    /**     * Remove the row whose index is r.     * The row is returned as a vector.     * @pre 0 <= r < height()<br>     * @post removes row r and returns it as a Vector     *     * @param r The index of the to-be-removed row.     * @return A vector of values once in the row.     */    public Vector removeRow(int r)    {	Assert.pre(0 <= r && r < height,"There is a row to be removed.");	Vector result = (Vector)rows.get(r);	height--;	rows.remove(r);	return result;    }    /**     * Remove a column, whose index is c.     * @pre 0 <= c < width<br>     * @post removes column c and returns it as a vector<br>     *     * @param c The index of the column to be removed.     * @return A vector of the values removed.     */    public Vector removeCol(int c)    {	Assert.pre(0 <= c && c < width,"There is a column to be removed.");	Vector result = new Vector(height);	width--;	for (int r = 0; r < height; r++)	{	    Vector theRow = (Vector)rows.get(r);	    result.add(theRow.get(c));	    theRow.remove(c);	}	return result;    }    /**     * Return the width of the matrix.     * @post returns number of columns in matrix<br>     *     * @return The number of columns in the matrix.     */    public int width()    {	return width;    }    /**     * Return the height of the matrix.     *     * @post returns number of rows in matrix<br>     *     * @return The number of rows in the matrix.     */    public int height()    {	return height;    }    /**     * Construct a string representation of the matrix.     * @post returns string description of matrix.<br>     *     * @return A string, representing the matrix.     */    public String toString()    {	StringBuffer s = new StringBuffer();	s.append("<Matrix:\n");	for (int r = 0; r < height; r++)	{	    for (int c = 0; c < width; c++)	    {		s.append("  <Row "+r+", Col "+c+", value=");		s.append(get(r,c)+">");	    }	    s.append("\n");	}	s.append(">");	return s.toString();    }}