Add Did You Mean Suggestion for Mistyped Commands #40

Thidas Senavirathna · Thidas Senavirathna · commit 2d8d90203116 · 2025-10-17T08:25:06.000+05:30
diff --git a/src/main/java/com/mycmd/App.java b/src/main/java/com/mycmd/App.java
@@ -35,8 +35,6 @@ public static void main(String[] args) {
                     System.out.println("Error: " + e.getMessage());
                 }
             } else {
-                System.out.println("'" + cmd + "' is not recognized as an internal or external command.");
-                // Suggest closest command
                 List<String> validCommands = new ArrayList<>(commands.keySet());
                 String suggestion = StringUtils.findClosest(cmd, validCommands);
                 if (suggestion != null && !suggestion.equals(cmd)) {
diff --git a/src/main/java/com/mycmd/StringUtils.java b/src/main/java/com/mycmd/StringUtils.java
@@ -32,6 +32,17 @@ public static String findClosest(String input, List<String> candidates) {
                 closest = candidate;
             }
         }
-        return closest;
+        // Only return a suggestion when the distance is small enough to be useful.
+        // A threshold of 2 works well for short typos (e.g. "di" -> "dir"),
+        // and we also allow a slightly larger threshold for longer candidates.
+        if (closest == null) return null;
+        int threshold = 2;
+        int len = Math.max(input.length(), closest.length());
+        // allow up to ~25% of the length as distance for long words (min 2)
+        int adaptive = Math.max(threshold, len / 4);
+        if (minDist <= adaptive) {
+            return closest;
+        }
+        return null;
     }
 }
diff --git a/target/maven-status/maven-compiler-plugin/compile/default-compile/inputFiles.lst b/target/maven-status/maven-compiler-plugin/compile/default-compile/inputFiles.lst
@@ -1,27 +1,28 @@
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\App.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\Command.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\CdCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\ClsCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\ColorCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\CopyCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\DateCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\DelCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\DirCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\EchoCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\ExitCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\HelpCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\HistoryCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\HostnameCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\LsCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\MkdirCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\MoveCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\PingCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\RmdirCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\TimeCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\TitleCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\TouchCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\TreeCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\TypeCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\VersionCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\commands\WhoamiCommand.java
-c:\Users\kgfga\MyCMD\src\main\java\com\mycmd\ShellContext.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\App.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\Command.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\CdCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\ClsCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\ColorCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\CopyCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\DateCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\DelCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\DirCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\EchoCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\ExitCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\HelpCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\HistoryCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\HostnameCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\LsCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\MkdirCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\MoveCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\PingCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\RmdirCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\TimeCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\TitleCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\TouchCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\TreeCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\TypeCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\VersionCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\commands\WhoamiCommand.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\ShellContext.java
+C:\Users\thidass\Desktop\gittest\MyCMD\src\main\java\com\mycmd\StringUtils.java

Original file line number	Diff line number	Diff line change
`@@ -35,8 +35,6 @@ public static void main(String[] args) {`
`35`	`35`	`System.out.println("Error: " + e.getMessage());`
`36`	`36`	`}`
`37`	`37`	`} else {`
`38`		`- System.out.println("'" + cmd + "' is not recognized as an internal or external command.");`
`39`		`- // Suggest closest command`
`40`	`38`	`List<String> validCommands = new ArrayList<>(commands.keySet());`
`41`	`39`	`String suggestion = StringUtils.findClosest(cmd, validCommands);`
`42`	`40`	`if (suggestion != null && !suggestion.equals(cmd)) {`
Original file line number	Diff line number	Diff line change
`@@ -32,6 +32,17 @@ public static String findClosest(String input, List<String> candidates) {`
`32`	`32`	`closest = candidate;`
`33`	`33`	`}`
`34`	`34`	`}`
`35`		`- return closest;`
	`35`	`+ // Only return a suggestion when the distance is small enough to be useful.`
	`36`	`+ // A threshold of 2 works well for short typos (e.g. "di" -> "dir"),`
	`37`	`+ // and we also allow a slightly larger threshold for longer candidates.`
	`38`	`+ if (closest == null) return null;`
	`39`	`+ int threshold = 2;`
	`40`	`+ int len = Math.max(input.length(), closest.length());`
	`41`	`+ // allow up to ~25% of the length as distance for long words (min 2)`
	`42`	`+ int adaptive = Math.max(threshold, len / 4);`
	`43`	`+ if (minDist <= adaptive) {`
	`44`	`+ return closest;`
	`45`	`+ }`
	`46`	`+ return null;`
`36`	`47`	`}`
`37`	`48`	`}`