EightPuzzle classes polished.

Author: RuedigerLunde

aima-core/src/main/java/aima/core/environment/eightpuzzle/EightPuzzleBoard.java

@@ -1,6 +1,7 @@
 package aima.core.environment.eightpuzzle;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 
 import aima.core.agent.Action;
@@ -11,7 +12,7 @@
  * @author Ravi Mohan
  * @author Ruediger Lunde
  */
-public class EightPuzzleBoard {
+public class EightPuzzleBoard implements Cloneable {
 
 	public static Action LEFT = new DynamicAction("Left");
 	public static Action RIGHT = new DynamicAction("Right");
@@ -27,13 +28,8 @@ public EightPuzzleBoard() {
 		state = new int[] { 5, 4, 0, 6, 1, 8, 7, 3, 2 };
 	}
 
-	public EightPuzzleBoard(int[] state) {
-		this.state = new int[state.length];
-		System.arraycopy(state, 0, this.state, 0, state.length);
-	}
-
-	public EightPuzzleBoard(EightPuzzleBoard copyBoard) {
-		this(copyBoard.getState());
+	public EightPuzzleBoard(int[] state) { state.clone();
+		this.state = state.clone();
 	}
 
 	public int[] getState() {
@@ -45,8 +41,8 @@ public int getValueAt(XYLocation loc) {
 	}
 
 	public XYLocation getLocationOf(int val) {
-		int absPos = getPositionOf(val);
-		return new XYLocation(getXCoord(absPos), getYCoord(absPos));
+		int pos = getPositionOf(val);
+		return new XYLocation(getXCoord(pos), getYCoord(pos));
 	}
 
 	public void moveGapRight() {
@@ -93,8 +89,8 @@ public void moveGapUp() {
 	public List<XYLocation> getPositions() {
 		ArrayList<XYLocation> result = new ArrayList<>(9);
 		for (int i = 0; i < 9; i++) {
-			int absPos = getPositionOf(i);
-			result.add(new XYLocation(getXCoord(absPos), getYCoord(absPos)));
+			int pos = getPositionOf(i);
+			result.add(new XYLocation(getXCoord(pos), getYCoord(pos)));
 		}
 		return result;
 	}
@@ -107,75 +103,69 @@ public void setBoard(List<XYLocation> locs) {
 
 	public boolean canMoveGap(Action action) {
 		boolean result = true;
-		int absPos = getPositionOf(0);
+		int pos = getPositionOf(0);
 		if (action.equals(LEFT))
-			result = (getXCoord(absPos) != 0);
+			result = (getXCoord(pos) != 0);
 		else if (action.equals(RIGHT))
-			result = (getXCoord(absPos) != 2);
+			result = (getXCoord(pos) != 2);
 		else if (action.equals(UP))
-			result = (getYCoord(absPos) != 0);
+			result = (getYCoord(pos) != 0);
 		else if (action.equals(DOWN))
-			result = (getYCoord(absPos) != 2);
+			result = (getYCoord(pos) != 2);
 		return result;
 	}
 
 	@Override
 	public boolean equals(Object o) {
 		if (o != null && getClass() == o.getClass()) {
 			EightPuzzleBoard aBoard = (EightPuzzleBoard) o;
-			for (int i = 0; i < 9; i++) {
-				if (state[i] != aBoard.state[i])
-					return false;
-			}
-			return true;
+			return Arrays.equals(state, aBoard.state);
 		}
 		return false;
 	}
 
 	@Override
 	public int hashCode() {
-		int result = 17;
-		for (int i = 0; i < 8; i++) {
-			int position = this.getPositionOf(i);
-			result = 37 * result + position;
-		}
-		return result;
+		return Arrays.hashCode(state);
 	}
 
 	@Override
 	public String toString() {
 		return state[0] + " " + state[1] + " " + state[2] + "\n"
-				+ state[3] + " " + state[4] + " " + state[5] + " " + "\n"
+				+ state[3] + " " + state[4] + " " + state[5] + "\n"
 				+ state[6] + " " + state[7] + " " + state[8];
 	}
 
+	@Override
+	public EightPuzzleBoard clone() {
+		EightPuzzleBoard result = null;
+		try {
+			result = (EightPuzzleBoard) super.clone();
+			result.state = result.state.clone();
+		} catch (CloneNotSupportedException e) {
+			e.printStackTrace(); // should never happen...
+		}
+		return result;
+	}
+
 	//
 	// PRIVATE METHODS
 	//
 
-	/**
-	 * Note: The graphic representation maps x values on row numbers (x-axis in
-	 * vertical direction).
-	 */
-	private int getXCoord(int absPos) {
-		return absPos % 3;
+	private int getXCoord(int pos) {
+		return pos % 3;
 	}
-
-	/**
-	 * Note: The graphic representation maps y values on column numbers (y-axis
-	 * in horizontal direction).
-	 */
-	private int getYCoord(int absPos) {
-		return absPos / 3;
+	
+	private int getYCoord(int pos) {
+		return pos / 3;
 	}
 
-	private int getAbsPosition(int x, int y) {
+	private int getPosition(int x, int y) {
 		return x + 3 * y;
 	}
 
 	private int getValueAt(int x, int y) {
-		// refactor this use either case or a div/mod soln
-		return state[getAbsPosition(x, y)];
+		return state[getPosition(x, y)];
 	}
 
 	private int getGapPosition() {
@@ -190,7 +180,7 @@ private int getPositionOf(int val) {
 	}
 
 	private void setValue(int x, int y, int val) {
-		int absPos = getAbsPosition(x, y);
-		state[absPos] = val;
+		int pos = getPosition(x, y);
+		state[pos] = val;
 	}
 }

aima-core/src/main/java/aima/core/environment/eightpuzzle/EightPuzzleFunctions.java

@@ -22,9 +22,9 @@ public static List<Action> getActions(EightPuzzleBoard state) {
 	}
 
 	public static EightPuzzleBoard getResult(EightPuzzleBoard state, Action action) {
-		EightPuzzleBoard result = new EightPuzzleBoard(state);
+		EightPuzzleBoard result = state.clone();
 
-		if (state.canMoveGap(action)) {
+		if (result.canMoveGap(action)) {
 			if (action == EightPuzzleBoard.UP)
 				result.moveGapUp();
 			else if (action == EightPuzzleBoard.DOWN)