Refactor ColorCommand execution logic for improved clarity and error handling

See #13, #18

Author: nihaltp

src/main/java/com/mycmd/commands/ColorCommand.java

@@ -8,19 +8,38 @@ public class ColorCommand implements Command {
     public void execute(String[] args, ShellContext context) {
         if (args.length == 1) {
             String color = args[0];
+
+            if (color.length() != 2) {
+                System.out.println("Usage: color <background><text>");
+                return;
+            }
+
             String background = String.valueOf(color.charAt(0));
             String text = String.valueOf(color.charAt(1));
 
-            if (background == text) {
+            if (background.equals(text)) {
                 return;
             }
 
-            int bgIndex = Integer.parseInt(background,16);
-            int fgIndex = Integer.parseInt(text,16);
+            int bgIndex, fgIndex;
+            try {
+                bgIndex = Integer.parseInt(background,16);
+                fgIndex = Integer.parseInt(text,16);
+            } catch (NumberFormatException e) {
+                System.out.println("Invalid color code. must use two hexadecimal digits.");
+                System.out.println("Example: color 0A");
+                return;
+            }
 
             String[] ansiForeground = {"30","34","32","36","31","35","33","37","90","94","92","96","91","95","93","97"};
             String[] ansiBackground = {"40","44","42","46","41","45","43","47","100","104","102","106","101","105","103","107"};
 
+            if (bgIndex >= ansiBackground.length || fgIndex >= ansiForeground.length) {
+                System.out.println("Invalid color code. must use two hexadecimal digits.");
+                System.out.println("Example: color 0A");
+                return;
+            }
+
             String bg = "\033[" + ansiBackground[bgIndex] + "m";
             String fg = "\033[" + ansiForeground[fgIndex] + "m";