feat: add runner.ps1 with PowerShell FileSystemWatcher watch mode

README.md

@@ -71,19 +71,22 @@ chmod +x runner.sh
 ./runner.sh --help
 ```
 
-### Windows
+### Windows (Command Prompt)
 
 ```cmd
 runner.bat HelloWorld.java
 runner.bat
 runner.bat HelloWorld.java --watch
 ```
 
-From PowerShell, prefix with `.\`:
+### Windows (PowerShell)
+
+`runner.ps1` uses `FileSystemWatcher` for event-based watch mode instead of polling.
 
 ```powershell
-.\runner.bat HelloWorld.java
-.\runner.bat HelloWorld.java --watch
+.\runner.ps1 HelloWorld.java
+.\runner.ps1
+.\runner.ps1 HelloWorld.java -Watch
 ```
 
 ---
@@ -187,8 +190,9 @@ java-runner/
 ├── .gitattributes
 ├── .gitignore
 ├── README.md
-├── runner.bat              # Windows script
-├── runner.sh               # Linux and macOS script
+├── runner.bat              # Windows (Command Prompt)
+├── runner.ps1              # Windows (PowerShell, event-based watch mode)
+├── runner.sh               # Linux and macOS
 ├── test.bat                # Test suite for Windows
 └── test.sh                 # Test suite for Linux and macOS
 ```
@@ -240,7 +244,7 @@ The `examples/` folder contains three files you can use to verify the setup or a
 - [x] Auto-detect test added to `test.sh` and `test.bat`
 - [x] GitHub Pages site with project documentation
 - [x] Clear screen between runs in watch mode
-- [ ] `runner.ps1` using PowerShell `FileSystemWatcher` for event-based watch mode on Windows
+- [x] `runner.ps1` using PowerShell `FileSystemWatcher` for event-based watch mode on Windows
 
 ### Phase 4 - Features
 

runner.ps1

@@ -0,0 +1,116 @@
+# java-runner - run Java exercises without an IDE (PowerShell)
+# Usage: .\runner.ps1 [File.java] [-Watch]
+
+param(
+    [string]$JavaFile = "",
+    [switch]$Watch,
+    [switch]$Help
+)
+
+if ($Help) {
+    Write-Host "Usage: .\runner.ps1 [File.java] [-Watch]"
+    Write-Host "  File.java   Java file to compile and run (optional if only one .java exists)"
+    Write-Host "  -Watch      Recompile and rerun on every file save (event-based)"
+    exit 0
+}
+
+# Auto-detect .java file
+if (-not $JavaFile) {
+    $found = @(Get-ChildItem -Path . -Filter "*.java" -File)
+
+    if ($found.Count -eq 0 -and (Test-Path ".\examples")) {
+        $found = @(Get-ChildItem -Path ".\examples" -Filter "*.java" -File)
+        if ($found.Count -gt 0) {
+            Write-Host "[INFO] No .java in current dir, searching examples\" -ForegroundColor Yellow
+        }
+    }
+
+    if ($found.Count -eq 1) {
+        $JavaFile = $found[0].FullName
+    } elseif ($found.Count -eq 0) {
+        Write-Host "[ERROR] No .java file found in current directory or examples\" -ForegroundColor Red
+        exit 1
+    } else {
+        Write-Host "[WARNING] Multiple .java files found. Please specify one:" -ForegroundColor Yellow
+        $found | ForEach-Object { Write-Host "  $($_.Name)" }
+        exit 1
+    }
+}
+
+if (-not (Test-Path $JavaFile)) {
+    Write-Host "[ERROR] File not found: $JavaFile" -ForegroundColor Red
+    exit 1
+}
+
+$JavaFile = (Resolve-Path $JavaFile).Path
+
+function Invoke-Run {
+    $className = [System.IO.Path]::GetFileNameWithoutExtension($JavaFile)
+    $tmpDir = Join-Path $env:TEMP ("java-runner-" + [System.IO.Path]::GetRandomFileName())
+    New-Item -ItemType Directory -Path $tmpDir -Force | Out-Null
+
+    Write-Host ""
+    Write-Host "[....] Compiling $className.java..." -ForegroundColor Cyan
+
+    $errFile = Join-Path $tmpDir "errors.txt"
+    & javac -d $tmpDir $JavaFile 2>$errFile
+    $compileExit = $LASTEXITCODE
+
+    if ($compileExit -ne 0) {
+        Write-Host "[FAIL] Compilation failed:" -ForegroundColor Red
+        Write-Host ""
+        Get-Content $errFile | ForEach-Object { Write-Host $_ }
+        Remove-Item -Recurse -Force $tmpDir
+        return $compileExit
+    }
+
+    Write-Host "[ OK ] Compiled successfully" -ForegroundColor Green
+    Write-Host "───────────────────────── output ─────────────────────────" -ForegroundColor Cyan
+
+    $sw = [System.Diagnostics.Stopwatch]::StartNew()
+    & java -cp $tmpDir $className
+    $javaExit = $LASTEXITCODE
+    $sw.Stop()
+    $elapsed = $sw.ElapsedMilliseconds
+
+    Write-Host "───────────────────────────────────────────────────────────" -ForegroundColor Cyan
+    if ($javaExit -ne 0) {
+        Write-Host "[FAIL] Finished in ${elapsed}ms (exit code $javaExit)" -ForegroundColor Red
+    } else {
+        Write-Host "[ OK ] Finished in ${elapsed}ms" -ForegroundColor Green
+    }
+    Write-Host ""
+
+    Remove-Item -Recurse -Force $tmpDir
+    return $javaExit
+}
+
+if ($Watch) {
+    Write-Host "[WATCH] Watch mode enabled - save the file to rerun" -ForegroundColor Yellow
+
+    $dir = Split-Path $JavaFile -Parent
+    $filename = Split-Path $JavaFile -Leaf
+
+    Clear-Host
+    Invoke-Run | Out-Null
+
+    $watcher = New-Object System.IO.FileSystemWatcher($dir, $filename)
+    $watcher.NotifyFilter = [System.IO.NotifyFilters]::LastWrite
+    $watcher.EnableRaisingEvents = $true
+
+    try {
+        while ($true) {
+            $result = $watcher.WaitForChanged([System.IO.WatcherChangeTypes]::Changed, 5000)
+            if (-not $result.TimedOut) {
+                Start-Sleep -Milliseconds 100
+                Clear-Host
+                Invoke-Run | Out-Null
+            }
+        }
+    } finally {
+        $watcher.Dispose()
+    }
+} else {
+    $exitCode = Invoke-Run
+    exit $exitCode
+}