Make fields final if possible to ensure immutability

src/main/java/appeng/client/gui/widgets/GuiImgButton.java

@@ -36,8 +36,8 @@ public class GuiImgButton extends GuiButton implements ITooltip
 	class EnumPair
 	{
 
-		Enum setting;
-		Enum value;
+		final Enum setting;
+		final Enum value;
 
 		EnumPair(Enum a, Enum b) {
 			setting = a;

src/main/java/appeng/client/gui/widgets/GuiProgressBar.java

@@ -14,7 +14,7 @@ public class GuiProgressBar extends GuiButton implements ITooltip
 		HORIZONTAL, VERTICAL
 	}
 
-	private IProgressProvider source;
+	private final IProgressProvider source;
 	private ResourceLocation texture;
 	private int fill_u;
 	private int fill_v;

src/main/java/appeng/client/gui/widgets/GuiTabButton.java

@@ -15,14 +15,14 @@ import appeng.client.texture.ExtraBlockTextures;
 public class GuiTabButton extends GuiButton implements ITooltip
 {
 
-	RenderItem itemRenderer;
+	final RenderItem itemRenderer;
 
 	int myIcon = -1;
 	public int hideEdge = 0;
 
 	ItemStack myItem;
 
-	String Msg;
+	final String Msg;
 
 	public void setVisibility(boolean vis)
 	{

src/main/java/appeng/client/gui/widgets/GuiToggleButton.java

@@ -11,11 +11,11 @@ import appeng.client.texture.ExtraBlockTextures;
 public class GuiToggleButton extends GuiButton implements ITooltip
 {
 
-	int iconIdxOn;
-	int iconIdxOff;
+	final int iconIdxOn;
+	final int iconIdxOff;
 
-	String Name;
-	String Hint;
+	final String Name;
+	final String Hint;
 
 	boolean on;
 

src/main/java/appeng/client/gui/widgets/MEGuiTextField.java

@@ -6,11 +6,11 @@ import net.minecraft.client.gui.GuiTextField;
 public class MEGuiTextField extends GuiTextField
 {
 
-	int posX;
-	int posY;
+	final int posX;
+	final int posY;
 
-	int myWidth;
-	int myHeight;
+	final int myWidth;
+	final int myHeight;
 
 	public MEGuiTextField(FontRenderer par1FontRenderer, int xPos, int yPos, int width, int height) {
 		super( par1FontRenderer, xPos, yPos, width, height );