fixed compiling issue

Author: Thidas Senavirathna

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

@@ -1,14 +1,32 @@
 package com.mycmd;
 
-import com.mycmd.ShellContext;
+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.
+ */
 public interface Command {
-    String getName();
-    String getDescription();
     /**
      * Execute the command.
-     * @param context shell context
-     * @param args command arguments
+     *
+     * @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(ShellContext context, String[] args) throws Exception;
-}
+    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.
+     */
+    default String usage() {
+        return "";
+    }
+}

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

@@ -1,68 +1,69 @@
 package com.mycmd.commands;
 
+import com.mycmd.Command;
 import com.mycmd.ShellContext;
+
+import java.io.IOException;
 import java.util.Map;
 
 public class AliasCommand implements Command {
     @Override
-    public void execute(String[] args, ShellContext context) {
-        if (args.length == 0) {
-            // List all aliases
+    public void execute(String[] args, ShellContext context) throws IOException {
+        // no args: list aliases
+        if (args == null || args.length == 0) {
             Map<String, String> aliases = context.getAliases();
             if (aliases.isEmpty()) {
                 System.out.println("No aliases defined.");
             } else {
-                System.out.println("Current aliases:");
-                for (Map.Entry<String, String> entry : aliases.entrySet()) {
-                    System.out.println("  " + entry.getKey() + "=\"" + entry.getValue() + "\"");
-                }
-            }
-        } else {
-            // Create alias: alias name="command" or alias name=command
-            String input = String.join(" ", args);
-            
-            if (!input.contains("=")) {
-                System.out.println("Usage: alias name=\"command\"");
-                System.out.println("Example: alias ll=\"dir /w\"");
-                return;
+                aliases.forEach((k, v) -> System.out.println(k + "=" + v));
             }
+            return;
+        }
 
-            String[] parts = input.split("=", 2);
+        // single arg of form name=command
+        if (args.length == 1 && args[0].contains("=")) {
+            String[] parts = args[0].split("=", 2);
             String name = parts[0].trim();
-            String command = parts[1].trim();
-
-            // Remove quotes if present
-            if (command.startsWith("\"") && command.endsWith("\"")) {
-                command = command.substring(1, command.length() - 1);
-            }
-
-            // Validate alias name
-            if (name.isEmpty() || name.contains(" ")) {
-                System.out.println("Error: Alias name cannot be empty or contain spaces.");
+            String cmd = parts[1].trim();
+            if (name.isEmpty() || cmd.isEmpty()) {
+                System.out.println("Invalid alias format. Usage: alias name=command");
                 return;
             }
+            context.addAlias(name, cmd);
+            System.out.println("Alias added: " + name + "=" + cmd);
+            return;
+        }
 
-            if (command.isEmpty()) {
-                System.out.println("Error: Alias command cannot be empty.");
-                return;
+        // multiple args: first is name, rest form command
+        if (args.length >= 2) {
+            String name = args[0];
+            StringBuilder sb = new StringBuilder();
+            for (int i = 1; i < args.length; i++) {
+                if (i > 1) sb.append(' ');
+                sb.append(args[i]);
             }
-
-            // Check for circular reference
-            if (command.split("\\s+")[0].equalsIgnoreCase(name)) {
-                System.out.println("Error: Cannot create circular alias reference.");
+            String cmd = sb.toString();
+            if (name.trim().isEmpty() || cmd.trim().isEmpty()) {
+                System.out.println("Invalid alias. Usage: alias name command... or alias name=command");
                 return;
             }
-
-            context.addAlias(name, command);
-            System.out.println("Alias created: " + name + "=\"" + command + "\"");
+            context.addAlias(name, cmd);
+            System.out.println("Alias added: " + name + "=" + cmd);
+            return;
         }
+
+        System.out.println("Invalid usage. Usage: alias [name=command] | alias [name command...]");
+    }
+
+    @Override
+    public String description() {
+        return "Create or list command aliases.";
     }
 
     @Override
-    public String getHelp() {
-        return "alias [name=\"command\"] - Create or list command aliases\n" +
-               "  alias                  - List all aliases\n" +
-               "  alias name=\"command\"   - Create new alias\n" +
-               "  Example: alias ll=\"dir /w\"";
+    public String usage() {
+        return "alias                 # list aliases\n" +
+               "alias name=command    # create alias\n" +
+               "alias name command... # create alias";
     }
 }

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

@@ -1,30 +1,36 @@
 package com.mycmd.commands;
 
+import com.mycmd.Command;
 import com.mycmd.ShellContext;
 
+import java.io.IOException;
+
 public class UnaliasCommand implements Command {
     @Override
-    public void execute(String[] args, ShellContext context) {
-        if (args.length == 0) {
-            System.out.println("Usage: unalias <name>");
-            System.out.println("Example: unalias ll");
+    public void execute(String[] args, ShellContext context) throws IOException {
+        if (args == null || args.length == 0) {
+            System.out.println("Usage: unalias name [name2 ...]");
             return;
         }
 
-        String aliasName = args[0].trim();
-
-        if (!context.hasAlias(aliasName)) {
-            System.out.println("Error: Alias '" + aliasName + "' not found.");
-            return;
+        for (String name : args) {
+            if (name == null || name.trim().isEmpty()) continue;
+            if (context.hasAlias(name)) {
+                context.removeAlias(name);
+                System.out.println("Removed alias: " + name);
+            } else {
+                System.out.println("Alias not found: " + name);
+            }
         }
+    }
 
-        context.removeAlias(aliasName);
-        System.out.println("Alias removed: " + aliasName);
+    @Override
+    public String description() {
+        return "Remove one or more aliases.";
     }
 
     @Override
-    public String getHelp() {
-        return "unalias <name> - Remove a command alias\n" +
-               "  Example: unalias ll";
+    public String usage() {
+        return "unalias name [name2 ...]";
     }
-}
+}