My開発メモ

enumを使う(Java)

『Javaで学ぶリファクタリング入門』p225〜p227 のコードを enum を使って書き直してみた。

Robot.java

import java.util.*;

public class Robot {
    private final String _name;
    private final Position _position = new Position( 0, 0 );
    private final Direction _direction = new Direction( 0, 1 );

    public Robot (String name) {
        _name = name;
    }

   /**
    * @param
    *   String commandSequence -- 例 "forward right forward left"
    */
    public void execute (String commandSequence) {
        StringTokenizer tokenizer = new StringTokenizer( commandSequence );
        try {
            while (tokenizer.hasMoreTokens()) {
                String token = tokenizer.nextToken();
                executeCommand( token );
            }
        } catch (InvalidCommandException e) {
            System.out.println("不正なコマンドです command: " + e.getMessage());
        }
    }

   /**
    * @param
    *   String commandString -- 例 "forward", "right" ...
    */
    public void executeCommand (String commandString) throws InvalidCommandException {
        Command command = Command.parseCommand( commandString );
        System.out.println("command:" + command);
        // System.out.println("Robot: _name: " + this._name );
        // System.out.println("Robot: _position: " + this._position._x + " " + this._position._y );
        // System.out.println("Robot: _direction: " + this._direction._x + " " + this._direction._y );
        
        // this -- Robot robot
        command.execute( this );
    }

    public void forward () {
        _position.relativeMove( _direction._x, _direction._y );
    }
    public void backward () {
        _position.relativeMove( -_direction._x, -_direction._y );
    }
    public void right () {
        _position.relativeMove( _direction._y, -_direction._x );
    }
    public void left () {
        _position.relativeMove( -_direction._y, _direction._x );
    }

    public String toString() {
        return "[ Robot: " + _name + " " +
            "position(" + _position._x + ", " + _position._y + "), " +
            "direction(" + _direction._x + ", " + _direction._y + ")"+ "]";
    }
}

Command.java

import java.util.HashMap;

public enum Command implements CommandExecute {
    FORWARD ("forward"){
        @Override public void execute (Robot robot) { robot.forward(); }
    },
    BACKWARD ("backward"){
        @Override public void execute (Robot robot) { robot.backward(); }
    },
    TURN_RIGHT ("right"){
        @Override public void execute (Robot robot) { robot.right(); }
    },
    TURN_LEFT ("left"){
        @Override public void execute (Robot robot) { robot.left(); }
    };

    private String name;

    private Command (String name) { this.name = name; }

    public String getName() { return this.name; }

    private static final HashMap<String, Command> _commandNameMap = new HashMap <> ();
    static {
        _commandNameMap.put( Command.FORWARD.getName(), FORWARD );
        _commandNameMap.put( Command.BACKWARD.getName(), BACKWARD );
        _commandNameMap.put( Command.TURN_RIGHT.getName(), TURN_RIGHT );
        _commandNameMap.put( Command.TURN_LEFT.getName(), TURN_LEFT );
    }

    public static Command parseCommand (String name) throws InvalidCommandException {
    	_commandNameMap.forEach( (str, command)  -> {
    		// System.out.println("str:" + str + " Command:" + command.name());
    	});
        if (! _commandNameMap.containsKey( name )) {
            throw new InvalidCommandException( name );
        }
        return _commandNameMap.get( name );
    }
}

Command.java

public interface CommandExecute {
	public void execute( Robot robot );
}

InvalidCommandException.java

public class InvalidCommandException extends Exception {
    public InvalidCommandException( String name ) {
        super( name );
    }

    public InvalidCommandException () {}
}

Direction.java

public class Direction {
    public int _x;
    public int _y;

    public Direction (int x, int y) {
        _x = x;
        _y = y;
    }

    public void setDirection (int x, int y) {
        _x = x;
        _y = y;
    }
}

Position.java

public class Position {
    public int _x;
    public int _y;
    public Position (int x, int y) {
        _x = x;
        _y = y;
    }
    public void relativeMove (int dx, int dy) {
        _x += dx;
        _y += dy;
    }
}

Main.java

public class Main {
    public static void main (String[] args) {
        Robot robot = new Robot( "Andrew" );
        System.out.println( robot.toString() );
        robot.execute( "forward right forward" );
        System.out.println( robot.toString() );
        robot.execute( "left backward left forward" );
        System.out.println( robot.toString() );
        robot.execute( "right backward forward farward" );
        System.out.println( robot.toString() );
    }
}