matrix.java

关于迭代器、构造器

// An implementation of a rectangular vector.
// (c) 1998, 2001 duane a. bailey
package 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();
    }

}