Symantec Visual Cafe for Java 2.5/symantec-visual-cafe-2.5-database-dev-edition.iso/Visual Cafe Pro v1.0/SOURCE.BIN/MatrixEnumeration.java

Java Source | 1997-06-19 | 4.2 KB | 210 lines

package symantec.itools.awt;


import java.util.Enumeration;


//     01/30/97    RKM    Integrated fix to hasMoreElements from [e-mail] (George Rome Borden IV)
//     03/27/97    RKM    Made class public, so peole could use it
//                    Made class final
//                    Tried to make some sense of protection on methods & members
//     04/17/97    LAB Added Don Haney's ([e-mail]) fix that addressed a NullPointerException in hasMoreElements().

/**
 * This class is used to enumerate Matrix objects. Enumeration is used to
 * sequentially scan through all the elements in the Matrix.
 * @see symantec.itools.awt.Matrix
 * @see java.util.Enumeration
 *
 * @version 1.0, Nov 26, 1996
 *
 * @author    Symantec
 *
 */

public final class MatrixEnumeration
    implements Enumeration
{
    //--------------------------------------------------
    // public constructors
    //--------------------------------------------------

    /**
     * Constructs a matrix enumerator.
     */
    public MatrixEnumeration(Matrix matrix)
    {
        m = matrix;
        started = false;
    }

    //--------------------------------------------------
    // public members
    //--------------------------------------------------

    /**
     * Returns true if more elements are available to enumerate.
     * A standard Java Enumeration interface method.
     * @return true if more elements available, false if done enumerating
     */
    public boolean hasMoreElements()
    {
        if (m == null)
            return false;
        if (started == false && m.o != null) return true;
        if (m.nextElt != null) return true;
        return hasMoreRows();
    }

    /**
     * Returns true if more rows are available to enumerate.
     */
    public boolean hasMoreRows()
    {
        if (m.nextRow == null)
        {
            return false;
        }

        Matrix n = m.nextRow;

        //find next row
        while(n.o == null && n.nextElt == null)
        {
            if ((n = n.nextRow) == null)  return false;
        }

        return true;
    }

    /**
     * Returns the next element.
     * A standard Java Enumeration interface method.
     */
    public Object nextElement()
    {
        if (!started)
        {
            started = true;

            if (m.o != null)
            {
                return m.o;
            }
        }

        if (m == null)
        {
            return null;
        }

        if (m.nextElt != null)
        {
            m = m.nextElt;
            return m.o;
        }

        if ((m = findNextRow()) == null)
        {
            return null;
        }

        return m.o;
    }

    /**
     * Returns the row number of the current element.
     */
    public int currRow()
    {
        return m.row;
    }

    /**
     * Returns the column number of the current element.
     */
    public int currCol()
    {
        return m.col;
    }

    /**
     * Skips enumeration ahead to the start of the next row.
     * @return the first element in the next row.
     */
    public Object nextRow()
    {
        m = findNextRow();

        return m.o;
    }

    /**
     * Skips enumeration ahead to the start of the given row.
     * @param r the row to skip ahead to. Must be greater than the current row
     * @return the first element in the given row
     */
    public Object advanceTo(int r)
        throws IllegalArgumentException
    {
        started = true;

        if (r < m.row || r == m.row)
        {
            throw new
               IllegalArgumentException("r must be greater than current row: r=" +
                                         r + "current row=" + m.row);
        }

        Matrix n = m;

        while (m.row < r)
        {
            m = findNextRow();

            if (m == null)
            {
                m = n;
                throw new
                   IllegalArgumentException("requested row too large: r=" + r);
            }
        }

        return m.o;
    }

    //--------------------------------------------------
    // private members
    //--------------------------------------------------

    private Matrix findNextRow()
    {
        started = true;
        Matrix n = m.nextRow;

        if (n == null)
        {
            return null;
        }

        //find next row
        while(n.o == null && n.nextElt == null)
        {
            if ((n = n.nextRow) == null)
            {
                return null;
            }
        }

        n = n.o != null  ?n  :n.nextElt;
        return n;
    }

    //--------------------------------------------------
    // private members
    //--------------------------------------------------

    private Matrix        m;
    private boolean    started;
}