Modify Command interface to include default methods

Updated the execute method to throw IOException and added default methods for description and usage.

Author: anshumanjadiya1102

src/main/java/com/mycmd/Command.java

@@ -1,5 +1,7 @@
 package com.mycmd;
 
+import java.io.IOException;
+
 /**
  * Represents a shell command that can be executed inside the MyCMD shell.
  * Implementations perform their operation when {@link #execute(String[], ShellContext)} is called.
@@ -8,19 +10,23 @@ public interface Command {
     /**
      * Execute the command.
      *
-     * <p>Implementations should perform all output to standard output or use the provided
-     * {@link ShellContext} for interactions that depend on the shell state (for example,
-     * changing the current directory).</p>
-     *
-     * @param args    command-line style arguments passed to the command. May be empty but
-     *                will not be null.
-     * @param context current shell context containing state such as the current working
-     *                directory. Implementations may read and/or modify this context.
-     * @throws Exception if the command cannot complete successfully. The caller (shell)
-     *                   is responsible for catching and reporting exceptions.
-     *
-     * @implNote Common concrete commands include `date` and `time` which simply print the
-     * current date/time to standard output. See their implementations for formatting details.
+     * @param args    command-line style arguments passed to the command. May be empty but will not be null.
+     * @param context current shell context containing state such as the current working directory.
+     * @throws IOException if the command cannot complete successfully.
+     */
+    void execute(String[] args, ShellContext context) throws IOException;
+
+    /**
+     * Short description of the command. Default is empty so existing implementations do not break.
+     */
+    default String description() {
+        return "";
+    }
+
+    /**
+     * Usage string for the command. Default is empty.
      */
-    void execute(String[] args, ShellContext context);
+    default String usage() {
+        return "";
+    }
 }