Add WhoamiCommand to display the current user's name

src/main/java/com/mycmd/App.java

@@ -51,6 +51,7 @@ private static void registerCommands(Map<String, Command> commands) {
         commands.put("help", new HelpCommand(commands));
         commands.put("exit", new ExitCommand());
         commands.put("ver", new VersionCommand());
+        commands.put("whoami", new WhoamiCommand());
         commands.put("touch", new TouchCommand());
         commands.put("time", new TimeCommand());
         commands.put("date", new DateCommand());

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

@@ -0,0 +1,11 @@
+package com.mycmd.commands;
+
+import com.mycmd.Command;
+import com.mycmd.ShellContext;
+
+public class WhoamiCommand implements Command {
+    @Override
+    public void execute(String[] args, ShellContext context) {
+        System.out.println(System.getProperty("user.name"));
+    }
+}