1) Command pattern 2) applyMask 3) switch statement

java/src/main/java/io/nayuki/qrcodegen/Button.java

@@ -0,0 +1,17 @@
+package io.nayuki.qrcodegen;
+
+public class Button {
+	public Command theCommand;
+
+	public Button(Command theCommand) {
+		setCommand(theCommand);
+	}
+
+	public void setCommand(Command newCommand) {
+		this.theCommand = newCommand;
+	}
+
+	public boolean pressed(int y, int x, int msk) {
+		return theCommand.excute(y, x, msk);
+	}
+}

java/src/main/java/io/nayuki/qrcodegen/Command.java

@@ -0,0 +1,5 @@
+package io.nayuki.qrcodegen;
+
+public interface Command {
+	public abstract boolean excute(int y, int x, int msk);
+}

java/src/main/java/io/nayuki/qrcodegen/Msk0.java

@@ -0,0 +1,7 @@
+package io.nayuki.qrcodegen;
+
+public class Msk0 {
+	public boolean operation(int y, int x, int msk) {
+		return ((x + y) % 2 == 0);
+	}
+}

java/src/main/java/io/nayuki/qrcodegen/QrCode.java

@@ -546,9 +546,15 @@ public final class QrCode {
 	private void applyMask(int msk) {
 		if (msk < 0 || msk > 7)
 			throw new IllegalArgumentException("Mask value out of range");
-		for (int y = 0; y < size; y++) {
+		for (int y = 0; y < size; y++) {	
 			for (int x = 0; x < size; x++) {
 				boolean invert;
+				Msk0 msk0 = new Msk0();
+				Command mskCommand = new msk0Command(msk0);
+				
+				Button button = new Button(mskCommand);
+				invert = button.pressed(y, x, msk);
+				/*
 				switch (msk) {
 				case 0:  invert = (x + y) % 2 == 0;                    break;
 				case 1:  invert = y % 2 == 0;                          break;
@@ -560,6 +566,7 @@ public final class QrCode {
 				case 7:  invert = ((x + y) % 2 + x * y % 3) % 2 == 0;  break;
 				default:  throw new AssertionError();
 				}
+				*/
 				modules[y][x] ^= invert & !isFunction[y][x];
 			}
 		}

java/src/main/java/io/nayuki/qrcodegen/msk0Command.java

@@ -0,0 +1,13 @@
+package io.nayuki.qrcodegen;
+
+public class msk0Command implements Command{
+	private Msk0 theMsk0;
+	
+	public msk0Command(Msk0 theMsk0) {
+		this.theMsk0 = theMsk0;
+	}
+	
+	public boolean excute(int y, int x, int msk) {
+		return theMsk0.operation(y, x, msk);
+	}
+}