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#1 SkimMilk  Icon User is offline

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Error message from dividing main method into another class.

Posted 10 April 2012 - 12:29 PM

I have two classes that I divided from a program of Checkers, and now I get this error message: "Exception in thread "main" java.lang.NoSuchMethodError: main"

Here is my class with the main:

import java.awt.Dimension;
import java.awt.Toolkit;

import javax.swing.JFrame;


public class CheckersApp {
	
	public static void main(String[] args) {
	      JFrame window = new JFrame("Checkers");
	      Checkers content = new Checkers();
	      window.setContentPane(content);
	      window.pack();
	      Dimension screensize = Toolkit.getDefaultToolkit().getScreenSize();
	      window.setLocation( (screensize.width - window.getWidth())/2,
	            (screensize.height - window.getHeight())/2 );
	      window.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
	      window.setResizable(false);  
	      window.setVisible(true);
	   }
}



Here is the second part of the program with the rest of the code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.ArrayList;


public class Checkers extends JPanel {
   
	
   private JButton newGameButton;  // Button for starting a new game.
   private JButton resignButton;   // Button that a player can use to end 
                                   // the game by resigning.
   
   private JLabel message;  // Label for displaying messages to the user.
   
   /**
    * The constructor creates the Board (which in turn creates and manages
    * the buttons and message label), adds all the components, and sets
    * the bounds of the components.  A null layout is used.  (This is
    * the only thing that is done in the main Checkers class.)
    */
   public Checkers() {
      
      setLayout(null);  // I will do the layout myself.
      setPreferredSize( new Dimension(350,250) );
      
      setBackground(new Color(0,150,0));  // Dark green background.
      
      /* Create the components and add them to the applet. */
      
      Board board = new Board();  // Note: The constructor for the
                                  //   board also creates the buttons
                                  //   and label.
      add(board);
      add(newGameButton);
      add(resignButton);
      add(message);
      
      /* Set the position and size of each component by calling
       its setBounds() method. */
      
      board.setBounds(20,20,164,164); // Note:  size MUST be 164-by-164 !
      newGameButton.setBounds(210, 60, 120, 30);
      resignButton.setBounds(210, 120, 120, 30);
      message.setBounds(0, 200, 350, 30);
      
   } // end constructor
   
// --------------------  Nested Classes -------------------------------
   /**
    * A CheckersMove object represents a move in the game of Checkers.
    * It holds the row and column of the piece that is to be moved
    * and the row and column of the square to which it is to be moved.
    * (This class makes no guarantee that the move is legal.)   
    */
   private static class CheckersMove {
      int fromRow, fromCol;  // Position of piece to be moved.
      int toRow, toCol;      // Square it is to move to.
      CheckersMove(int r1, int c1, int r2, int c2) {
              // Constructor.  Just set the values of the instance variables.
         fromRow = r1;
         fromCol = c1;
         toRow = r2;
         toCol = c2;
      }
      boolean isJump() {
             // Test whether this move is a jump.  It is assumed that
             // the move is legal.  In a jump, the piece moves two
             // rows.  (In a regular move, it only moves one row.)
         return (fromRow - toRow == 2 || fromRow - toRow == -2);
      }
   }  // end class CheckersMove.
   
   
   
   /**
    * This panel displays a 160-by-160 checkerboard pattern with
    * a 2-pixel black border.  It is assumed that the size of the
    * panel is set to exactly 164-by-164 pixels.  This class does
    * the work of letting the users play checkers, and it displays
    * the checkerboard.
    */
   private class Board extends JPanel implements ActionListener, MouseListener {
      
      
      CheckersData board;  // The data for the checkers board is kept here.
                           //    This board is also responsible for generating
                           //    lists of legal moves.
      
      boolean gameInProgress; // Is a game currently in progress?
      
      /* The next three variables are valid only when the game is in progress. */
      
      int currentPlayer;      // Whose turn is it now?  The possible values
                              //    are CheckersData.RED and CheckersData.BLACK.
      
      int selectedRow, selectedCol;  // If the current player has selected a piece to
                                     //     move, these give the row and column
                                     //     containing that piece.  If no piece is
                                     //     yet selected, then selectedRow is -1.
      
      CheckersMove[] legalMoves;  // An array containing the legal moves for the
                                  //   current player.
      

      /**
       * Constructor.  Create the buttons and label.  Listens for mouse
        * clicks and for clicks on the buttons.  Create the board and
        * start the first game.
       */
      Board() {
         setBackground(Color.BLACK);
         addMouseListener(this);
         resignButton = new JButton("Resign");
         resignButton.addActionListener(this);
         newGameButton = new JButton("New Game");
         newGameButton.addActionListener(this);
         message = new JLabel("",JLabel.CENTER);
         message.setFont(new  Font("Serif", Font.BOLD, 14));
         message.setForeground(Color.green);
         board = new CheckersData();
         doNewGame();
      }
      
      
      /**
       * Respond to user's click on one of the two buttons.
       */
      public void actionPerformed(ActionEvent evt) {
         Object src = evt.getSource();
         if (src == newGameButton)
            doNewGame();
         else if (src == resignButton)
            doResign();
      }
      
      
      /**
       * Start a new game
       */
      void doNewGame() {
         if (gameInProgress == true) {
               // This should not be possible, but it doens't hurt to check.
            message.setText("Finish the current game first!");
            return;
         }
         board.setUpGame();   // Set up the pieces.
         currentPlayer = CheckersData.RED;   // RED moves first.
         legalMoves = board.getLegalMoves(CheckersData.RED);  // Get RED's legal moves.
         selectedRow = -1;   // RED has not yet selected a piece to move.
         message.setText("Red:  Make your move.");
         gameInProgress = true;
         newGameButton.setEnabled(false);
         resignButton.setEnabled(true);
         repaint();
      }
      
      
      /**
       * Current player resigns.  Game ends.  Opponent wins.
       */
      void doResign() {
         if (gameInProgress == false) {  // Should be impossible.
            message.setText("There is no game in progress!");
            return;
         }
         if (currentPlayer == CheckersData.RED)
            gameOver("RED resigns.  BLACK wins.");
         else
            gameOver("BLACK resigns.  RED wins.");
      }
      
      
      /**
       * The game ends.  The parameter, str, is displayed as a message
       * to the user.  The states of the buttons are adjusted so players
       * can start a new game.  This method is called when the game
       * ends at any point in this class.
       */
      void gameOver(String str) {
         message.setText(str);
         newGameButton.setEnabled(true);
         resignButton.setEnabled(false);
         gameInProgress = false;
      }
      
      
      /**
       * This is called by mousePressed() when a player clicks on the
       * square in the specified row and col.  It has already been checked
       * that a game is, in fact, in progress.
       */
      void doClickSquare(int row, int col) {
         
         /* If the player clicked on one of the pieces that the player
          can move, mark this row and col as selected and return.  (This
          might change a previous selection.)  Reset the message, in
          case it was previously displaying an error message. */
         
         for (int i = 0; i < legalMoves.length; i++)
            if (legalMoves[i].fromRow == row && legalMoves[i].fromCol == col) {
               selectedRow = row;
               selectedCol = col;
               if (currentPlayer == CheckersData.RED)
                  message.setText("RED:  Make your move.");
               else
                  message.setText("BLACK:  Make your move.");
               repaint();
               return;
            }
         
         /* If no piece has been selected to be moved, the user must first
          select a piece.  Show an error message and return. */
         
         if (selectedRow < 0) {
            message.setText("Click the piece you want to move.");
            return;
         }
         
         /* If the user clicked on a square where the selected piece can be
          legally moved, then make the move and return. */
         
         for (int i = 0; i < legalMoves.length; i++)
            if (legalMoves[i].fromRow == selectedRow && legalMoves[i].fromCol == selectedCol
                  && legalMoves[i].toRow == row && legalMoves[i].toCol == col) {
               doMakeMove(legalMoves[i]);
               return;
            }
         
         /* If we get to this point, there is a piece selected, and the square where
          the user just clicked is not one where that piece can be legally moved.
          Show an error message. */
         
         message.setText("Click the square you want to move to.");
         
      }  // end doClickSquare()
      
      
      /**
       * This is called when the current player has chosen the specified
       * move.  Make the move, and then either end or continue the game
       * appropriately.
       */
      void doMakeMove(CheckersMove move) {
         
         board.makeMove(move);
         
         /* If the move was a jump, it's possible that the player has another
          jump.  Check for legal jumps starting from the square that the player
          just moved to.  If there are any, the player must jump.  The same
          player continues moving.
          */
         
         if (move.isJump()) {
            legalMoves = board.getLegalJumpsFrom(currentPlayer,move.toRow,move.toCol);
            if (legalMoves != null) {
               if (currentPlayer == CheckersData.RED)
                  message.setText("RED:  You must continue jumping.");
               else
                  message.setText("BLACK:  You must continue jumping.");
               selectedRow = move.toRow;  // Since only one piece can be moved, select it.
               selectedCol = move.toCol;
               repaint();
               return;
            }
         }
         
         /* The current player's turn is ended, so change to the other player.
          Get that player's legal moves.  If the player has no legal moves,
          then the game ends. */
         
         if (currentPlayer == CheckersData.RED) {
            currentPlayer = CheckersData.BLACK;
            legalMoves = board.getLegalMoves(currentPlayer);
            if (legalMoves == null)
               gameOver("BLACK has no moves.  RED wins.");
            else if (legalMoves[0].isJump())
               message.setText("BLACK:  Make your move.  You must jump.");
            else
               message.setText("BLACK:  Make your move.");
         }
         else {
            currentPlayer = CheckersData.RED;
            legalMoves = board.getLegalMoves(currentPlayer);
            if (legalMoves == null)
               gameOver("RED has no moves.  BLACK wins.");
            else if (legalMoves[0].isJump())
               message.setText("RED:  Make your move.  You must jump.");
            else
               message.setText("RED:  Make your move.");
         }
         
         /* Set selectedRow = -1 to record that the player has not yet selected
          a piece to move. */
         
         selectedRow = -1;
         
         /* As a courtesy to the user, if all legal moves use the same piece, then
          select that piece automatically so the use won't have to click on it
          to select it. */
         
         if (legalMoves != null) {
            boolean sameStartSquare = true;
            for (int i = 1; i < legalMoves.length; i++)
               if (legalMoves[i].fromRow != legalMoves[0].fromRow
                     || legalMoves[i].fromCol != legalMoves[0].fromCol) {
                  sameStartSquare = false;
                  break;
               }
            if (sameStartSquare) {
               selectedRow = legalMoves[0].fromRow;
               selectedCol = legalMoves[0].fromCol;
            }
         }
         
         /* Make sure the board is redrawn in its new state. */
         
         repaint();
         
      }  // end doMakeMove();
      
      
      /**
       * Draw  checkerboard pattern in gray and lightGray.  Draw the
       * checkers.  If a game is in progress, hilite the legal moves.
       */
      public void paintComponent(Graphics g) {
         
         /* Draw a two-pixel black border around the edges of the canvas. */
         
         g.setColor(Color.black);
         g.drawRect(0,0,getSize().width-1,getSize().height-1);
         g.drawRect(1,1,getSize().width-3,getSize().height-3);
         
         /* Draw the squares of the checkerboard and the checkers. */
         
         for (int row = 0; row < 8; row++) {
            for (int col = 0; col < 8; col++) {
               if ( row % 2 == col % 2 )
                  g.setColor(Color.LIGHT_GRAY);
               else
                  g.setColor(Color.GRAY);
               g.fillRect(2 + col*20, 2 + row*20, 20, 20);
               switch (board.pieceAt(row,col)) {
               case CheckersData.RED:
                  g.setColor(Color.RED);
                  g.fillOval(4 + col*20, 4 + row*20, 15, 15);
                  break;
               case CheckersData.BLACK:
                  g.setColor(Color.BLACK);
                  g.fillOval(4 + col*20, 4 + row*20, 15, 15);
                  break;
               case CheckersData.RED_KING:
                  g.setColor(Color.RED);
                  g.fillOval(4 + col*20, 4 + row*20, 15, 15);
                  g.setColor(Color.WHITE);
                  g.drawString("K", 7 + col*20, 16 + row*20);
                  break;
               case CheckersData.BLACK_KING:
                  g.setColor(Color.BLACK);
                  g.fillOval(4 + col*20, 4 + row*20, 15, 15);
                  g.setColor(Color.WHITE);
                  g.drawString("K", 7 + col*20, 16 + row*20);
                  break;
               }
            }
         }
         
         /* If a game is in progress, hilite the legal moves.   Note that legalMoves
          is never null while a game is in progress. */      
         
         if (gameInProgress) {
               /* First, draw a 2-pixel cyan border around the pieces that can be moved. */
            g.setColor(Color.cyan);
            for (int i = 0; i < legalMoves.length; i++) {
               g.drawRect(2 + legalMoves[i].fromCol*20, 2 + legalMoves[i].fromRow*20, 19, 19);
               g.drawRect(3 + legalMoves[i].fromCol*20, 3 + legalMoves[i].fromRow*20, 17, 17);
            }
               /* If a piece is selected for moving (i.e. if selectedRow >= 0), then
                draw a 2-pixel white border around that piece and draw green borders 
                around each square that that piece can be moved to. */
            if (selectedRow >= 0) {
               g.setColor(Color.white);
               g.drawRect(2 + selectedCol*20, 2 + selectedRow*20, 19, 19);
               g.drawRect(3 + selectedCol*20, 3 + selectedRow*20, 17, 17);
               g.setColor(Color.green);
               for (int i = 0; i < legalMoves.length; i++) {
                  if (legalMoves[i].fromCol == selectedCol && legalMoves[i].fromRow == selectedRow) {
                     g.drawRect(2 + legalMoves[i].toCol*20, 2 + legalMoves[i].toRow*20, 19, 19);
                     g.drawRect(3 + legalMoves[i].toCol*20, 3 + legalMoves[i].toRow*20, 17, 17);
                  }
               }
            }
         }

      }  // end paintComponent()
      
      
      /**
       * Respond to a user click on the board.  If no game is in progress, show 
       * an error message.  Otherwise, find the row and column that the user 
       * clicked and call doClickSquare() to handle it.
       */
      public void mousePressed(MouseEvent evt) {
         if (gameInProgress == false)
            message.setText("Click \"New Game\" to start a new game.");
         else {
            int col = (evt.getX() - 2) / 20;
            int row = (evt.getY() - 2) / 20;
            if (col >= 0 && col < 8 && row >= 0 && row < 8)
               doClickSquare(row,col);
         }
      }
      
      
      public void mouseReleased(MouseEvent evt) { }
      public void mouseClicked(MouseEvent evt) { }
      public void mouseEntered(MouseEvent evt) { }
      public void mouseExited(MouseEvent evt) { }
      
      
   }  // end class Board
   
   
   
   /**
    * An object of this class holds data about a game of checkers.
    * It knows what kind of piece is on each square of the checkerboard.
    * Note that RED moves "up" the board (i.e. row number decreases)
    * while BLACK moves "down" the board (i.e. row number increases).
    * Methods are provided to return lists of available legal moves.
    */
   private static class CheckersData {
      
      /*  The following constants represent the possible contents of a square
          on the board.  The constants RED and BLACK also represent players
          in the game. */

      static final int
                EMPTY = 0,
                RED = 1,
                RED_KING = 2,
                BLACK = 3,
                BLACK_KING = 4;
      
      
      int[][] board;  // board[r][c] is the contents of row r, column c.  
      
      
      /**
       * Constructor.  Create the board and set it up for a new game.
       */
      CheckersData() {
         board = new int[8][8];
         setUpGame();
      }
      
      
      /**
       * Set up the board with checkers in position for the beginning
       * of a game.  Note that checkers can only be found in squares
       * that satisfy  row % 2 == col % 2.  At the start of the game,
       * all such squares in the first three rows contain black squares
       * and all such squares in the last three rows contain red squares.
       */
      void setUpGame() {
         for (int row = 0; row < 8; row++) {
            for (int col = 0; col < 8; col++) {
               if ( row % 2 == col % 2 ) {
                  if (row < 3)
                     board[row][col] = BLACK;
                  else if (row > 4)
                     board[row][col] = RED;
                  else
                     board[row][col] = EMPTY;
               }
               else {
                  board[row][col] = EMPTY;
               }
            }
         }
      }  // end setUpGame()
      
      
      /**
       * Return the contents of the square in the specified row and column.
       */
      int pieceAt(int row, int col) {
         return board[row][col];
      }
            
      
      /**
       * Make the specified move.  It is assumed that move
       * is non-null and that the move it represents is legal.
       */
      void makeMove(CheckersMove move) {
         makeMove(move.fromRow, move.fromCol, move.toRow, move.toCol);
      }
      
      
      /**
       * Make the move from (fromRow,fromCol) to (toRow,toCol).  It is
       * assumed that this move is legal.  If the move is a jump, the
       * jumped piece is removed from the board.  If a piece moves
       * the last row on the opponent's side of the board, the 
       * piece becomes a king.
       */
      void makeMove(int fromRow, int fromCol, int toRow, int toCol) {
         board[toRow][toCol] = board[fromRow][fromCol];
         board[fromRow][fromCol] = EMPTY;
         if (fromRow - toRow == 2 || fromRow - toRow == -2) {
            // The move is a jump.  Remove the jumped piece from the board.
            int jumpRow = (fromRow + toRow) / 2;  // Row of the jumped piece.
            int jumpCol = (fromCol + toCol) / 2;  // Column of the jumped piece.
            board[jumpRow][jumpCol] = EMPTY;
         }
         if (toRow == 0 && board[toRow][toCol] == RED)
            board[toRow][toCol] = RED_KING;
         if (toRow == 7 && board[toRow][toCol] == BLACK)
            board[toRow][toCol] = BLACK_KING;
      }
      
      /**
       * Return an array containing all the legal CheckersMoves
       * for the specified player on the current board.  If the player
       * has no legal moves, null is returned.  The value of player
       * should be one of the constants RED or BLACK; if not, null
       * is returned.  If the returned value is non-null, it consists
       * entirely of jump moves or entirely of regular moves, since
       * if the player can jump, only jumps are legal moves.
       */
      CheckersMove[] getLegalMoves(int player) {
         
         if (player != RED && player != BLACK)
            return null;
         
         int playerKing;  // The constant representing a King belonging to player.
         if (player == RED)
            playerKing = RED_KING;
         else
            playerKing = BLACK_KING;
         
         ArrayList<CheckersMove> moves = new ArrayList<CheckersMove>();  // Moves will be stored in this list.
         
         /*  First, check for any possible jumps.  Look at each square on the board.
          If that square contains one of the player's pieces, look at a possible
          jump in each of the four directions from that square.  If there is 
          a legal jump in that direction, put it in the moves ArrayList.
          */
         
         for (int row = 0; row < 8; row++) {
            for (int col = 0; col < 8; col++) {
               if (board[row][col] == player || board[row][col] == playerKing) {
                  if (canJump(player, row, col, row+1, col+1, row+2, col+2))
                     moves.add(new CheckersMove(row, col, row+2, col+2));
                  if (canJump(player, row, col, row-1, col+1, row-2, col+2))
                     moves.add(new CheckersMove(row, col, row-2, col+2));
                  if (canJump(player, row, col, row+1, col-1, row+2, col-2))
                     moves.add(new CheckersMove(row, col, row+2, col-2));
                  if (canJump(player, row, col, row-1, col-1, row-2, col-2))
                     moves.add(new CheckersMove(row, col, row-2, col-2));
               }
            }
         }
         
         /*  If any jump moves were found, then the user must jump, so we don't 
          add any regular moves.  However, if no jumps were found, check for
          any legal regular moves.  Look at each square on the board.
          If that square contains one of the player's pieces, look at a possible
          move in each of the four directions from that square.  If there is 
          a legal move in that direction, put it in the moves ArrayList.
          */
         
         if (moves.size() == 0) {
            for (int row = 0; row < 8; row++) {
               for (int col = 0; col < 8; col++) {
                  if (board[row][col] == player || board[row][col] == playerKing) {
                     if (canMove(player,row,col,row+1,col+1))
                        moves.add(new CheckersMove(row,col,row+1,col+1));
                     if (canMove(player,row,col,row-1,col+1))
                        moves.add(new CheckersMove(row,col,row-1,col+1));
                     if (canMove(player,row,col,row+1,col-1))
                        moves.add(new CheckersMove(row,col,row+1,col-1));
                     if (canMove(player,row,col,row-1,col-1))
                        moves.add(new CheckersMove(row,col,row-1,col-1));
                  }
               }
            }
         }
         
         /* If no legal moves have been found, return null.  Otherwise, create
          an array just big enough to hold all the legal moves, copy the
          legal moves from the ArrayList into the array, and return the array. */
         
         if (moves.size() == 0)
            return null;
         else {
            CheckersMove[] moveArray = new CheckersMove[moves.size()];
            for (int i = 0; i < moves.size(); i++)
               moveArray[i] = moves.get(i);
            return moveArray;
         }
         
      }  // end getLegalMoves
      
      
      /**
       * Return a list of the legal jumps that the specified player can
       * make starting from the specified row and column.  If no such
       * jumps are possible, null is returned.  The logic is similar
       * to the logic of the getLegalMoves() method.
       */
      CheckersMove[] getLegalJumpsFrom(int player, int row, int col) {
         if (player != RED && player != BLACK)
            return null;
         int playerKing;  // The constant representing a King belonging to player.
         if (player == RED)
            playerKing = RED_KING;
         else
            playerKing = BLACK_KING;
         ArrayList<CheckersMove> moves = new ArrayList<CheckersMove>();  // The legal jumps will be stored in this list.
         if (board[row][col] == player || board[row][col] == playerKing) {
            if (canJump(player, row, col, row+1, col+1, row+2, col+2))
               moves.add(new CheckersMove(row, col, row+2, col+2));
            if (canJump(player, row, col, row-1, col+1, row-2, col+2))
               moves.add(new CheckersMove(row, col, row-2, col+2));
            if (canJump(player, row, col, row+1, col-1, row+2, col-2))
               moves.add(new CheckersMove(row, col, row+2, col-2));
            if (canJump(player, row, col, row-1, col-1, row-2, col-2))
               moves.add(new CheckersMove(row, col, row-2, col-2));
         }
         if (moves.size() == 0)
            return null;
         else {
            CheckersMove[] moveArray = new CheckersMove[moves.size()];
            for (int i = 0; i < moves.size(); i++)
               moveArray[i] = moves.get(i);
            return moveArray;
         }
      }  // end getLegalMovesFrom()
      
      
      /**
       * This is called by the two previous methods to check whether the
       * player can legally jump from (r1,c1) to (r3,c3).  It is assumed
       * that the player has a piece at (r1,c1), that (r3,c3) is a position
       * that is 2 rows and 2 columns distant from (r1,c1) and that 
       * (r2,c2) is the square between (r1,c1) and (r3,c3).
       */
      private boolean canJump(int player, int r1, int c1, int r2, int c2, int r3, int c3) {
         
         if (r3 < 0 || r3 >= 8 || c3 < 0 || c3 >= 8)
            return false;  // (r3,c3) is off the board.
         
         if (board[r3][c3] != EMPTY)
            return false;  // (r3,c3) already contains a piece.
         
         if (player == RED) {
            if (board[r1][c1] == RED && r3 > r1)
               return false;  // Regular red piece can only move  up.
            if (board[r2][c2] != BLACK && board[r2][c2] != BLACK_KING)
               return false;  // There is no black piece to jump.
            return true;  // The jump is legal.
         }
         else {
            if (board[r1][c1] == BLACK && r3 < r1)
               return false;  // Regular black piece can only move downn.
            if (board[r2][c2] != RED && board[r2][c2] != RED_KING)
               return false;  // There is no red piece to jump.
            return true;  // The jump is legal.
         }
         
      }  // end canJump()
      
      
      /**
       * This is called by the getLegalMoves() method to determine whether
       * the player can legally move from (r1,c1) to (r2,c2).  It is
       * assumed that (r1,r2) contains one of the player's pieces and
       * that (r2,c2) is a neighboring square.
       */
      private boolean canMove(int player, int r1, int c1, int r2, int c2) {
         
         if (r2 < 0 || r2 >= 8 || c2 < 0 || c2 >= 8)
            return false;  // (r2,c2) is off the board.
         
         if (board[r2][c2] != EMPTY)
            return false;  // (r2,c2) already contains a piece.
         
         if (player == RED) {
            if (board[r1][c1] == RED && r2 > r1)
               return false;  // Regular red piece can only move down.
            return true;  // The move is legal.
         }
         else {
            if (board[r1][c1] == BLACK && r2 < r1)
               return false;  // Regular black piece can only move up.
            return true;  // The move is legal.
         }
         
      }  // end canMove()         
   } // end class CheckersData      
} // end class Checkers



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Replies To: Error message from dividing main method into another class.

#2 AVReidy  Icon User is offline

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Re: Error message from dividing main method into another class.

Posted 10 April 2012 - 12:54 PM

What do you mean by "divided"?
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#3 SkimMilk  Icon User is offline

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Re: Error message from dividing main method into another class.

Posted 10 April 2012 - 01:12 PM

I moved the main class from the Checkers class into CheckersApp class. When I try to compile and run the program it throws me that error message. I would like to know how to correct that. Thank you.
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#4 GregBrannon  Icon User is offline

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Re: Error message from dividing main method into another class.

Posted 10 April 2012 - 01:22 PM

So your Checkers class used to have a main() method, and now it doesn't. That's causing the compiler confusion, but that can be easily corrected. How are you compiling and running. If you're doing it at the command line, show us the commands you're using. You should be compiling CheckersApp which should be in a file called CheckersApp.java, because that's where the main() method is.
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#5 SkimMilk  Icon User is offline

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Re: Error message from dividing main method into another class.

Posted 11 April 2012 - 08:34 AM

I'm actually using Eclipse to compile and run my programs. The main method used to be in the Checkers class but I then moved it into CheckersApp class. I wanted to experiment and try creating a separate main method class from the rest of the code, if that makes any sense...
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#6 GregBrannon  Icon User is offline

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Re: Error message from dividing main method into another class.

Posted 11 April 2012 - 10:49 AM

Sure it makes sense. I've done much more radical things in Eclipse, and it's never gotten confused unless I've tried to do something incorrect, like trying to force it to compile and run a class without a main method in it.

You would get the error message if Eclipse allowed you the option to compile and run Checkers after removing its main() method. That's not the typical behavior I've observed, but it must be possible.

To fix: In the project explorer, if you right click on the class file that now has the main() method (CheckersApp) and select run (from my lousy memory, so I may not have it exactly right) then run as an application, all should be fine. If you're still getting the error message, or you're not getting the "run as an application" option, then something's messed, and I can't imagine what that might be based on what you've shown us. You may have to change the run configurations for that file if they're not updating to reflect that it now has a main() method.
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#7 SkimMilk  Icon User is offline

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Re: Error message from dividing main method into another class.

Posted 11 April 2012 - 11:52 AM

I don't know how but I got it to run now. Funny how things work out of no where sometimes >.< Thanks for you help anyways.
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#8 SkimMilk  Icon User is offline

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Re: Error message from dividing main method into another class.

Posted 12 April 2012 - 11:36 AM

Now I'm having a problem with the class CheckersApp. When I try to rename the file and class to SimpleCheckersGUI it throws me an error saying that there is no method for Checkers(). Why will it work if I name the class CheckersApp, but doesn't work when I name it SimpleCheckersGUI?
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#9 GregBrannon  Icon User is offline

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Re: Error message from dividing main method into another class.

Posted 12 April 2012 - 11:44 AM

Post the exact error message (copied and pasted) and the source code to which the error code applies.
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