[BAEL-8962] resolve review

Author: mohibul-telemagic

core-java-modules/core-java-compiler/pom.xml

@@ -25,6 +25,11 @@
             <artifactId>slf4j-api</artifactId>
             <version>${org.slf4j.version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.github.stefanbirkner</groupId>
+            <artifactId>system-lambda</artifactId>
+            <version>1.2.1</version>
+        </dependency>
     </dependencies>
 
     <properties>

core-java-modules/core-java-compiler/src/main/java/com/baeldung/compilerApi/JavaCompilerApiDemo.java

@@ -93,10 +93,10 @@ private boolean compile(Iterable<? extends JavaFileObject> compilationUnits) {
 
 
         JavaCompiler.CompilationTask task = compiler.getTask(
-                null,                       // Writer for compiler output
+                null,                   // Writer for compiler output
                 standardFileManager,        // File manager
                 diagnostics,                // Diagnostic listener
-                null,                    // Compiler options
+                null,                       // Compiler options
                 null,                       // Classes to be processed by annotation processors
                 compilationUnits            // Compilation units
         );
@@ -111,8 +111,9 @@ private boolean compile(Iterable<? extends JavaFileObject> compilationUnits) {
         return success;
     }
 
+// Add this method to JavaCompilerUtils
     /**
-     * Loads and executes the main method of a compiled class.
+     * Loads and executes the main method of a compiled class, capturing and returning the output.
      *
      * @param className The fully qualified name of the class to run
      * @param args Arguments to pass to the main method

core-java-modules/core-java-compiler/src/main/java/com/baeldung/compilerApi/JavaCompilerUtils.java

@@ -9,6 +9,8 @@
 import java.nio.file.Path;
 import java.nio.file.Paths;
 
+import static com.github.stefanbirkner.systemlambda.SystemLambda.tapSystemErr;
+import static com.github.stefanbirkner.systemlambda.SystemLambda.tapSystemOut;
 import static org.junit.jupiter.api.Assertions.*;
 
 public class JavaCompilerTest {
@@ -17,8 +19,6 @@ public class JavaCompilerTest {
     static Path tempDir;
 
     private JavaCompilerUtils compilerUtil;
-    private final ByteArrayOutputStream outputCaptor = new ByteArrayOutputStream();
-    private PrintStream standardOut;
 
     @BeforeEach
     void setUp() throws Exception {
@@ -28,20 +28,10 @@ void setUp() throws Exception {
 
         // Initialize the compiler util with the output directory
         compilerUtil = new JavaCompilerUtils(outputDir);
-
-        // Set up System.out capture
-        standardOut = System.out;
-        System.setOut(new PrintStream(outputCaptor));
-    }
-
-    @AfterEach
-    void tearDown() {
-        // Restore System.out
-        System.setOut(standardOut);
     }
 
     @Test
-    void testCompileFromString_Success() {
+    void given_simpleHelloWorldClass_when_compiledFromString_then_compilationSucceeds() {
         // Simple "Hello World" class
         String className = "HelloWorld";
         String sourceCode = "public class HelloWorld {\n" +
@@ -60,7 +50,7 @@ void testCompileFromString_Success() {
     }
 
     @Test
-    void testCompileFromString_WithPackage() {
+    void given_classWithPackage_when_compiledFromString_then_compilationSucceedsInPackageDirectory() {
         // Class with a package
         String className = "com.example.PackagedClass";
         String sourceCode = "package com.example;\n\n" +
@@ -81,7 +71,7 @@ void testCompileFromString_WithPackage() {
     }
 
     @Test
-    void testCompileFromString_CompilationError() {
+    void given_classWithSyntaxError_when_compiledFromString_then_compilationFails() {
         // Class with syntax error (missing semicolon)
         String className = "ErrorClass";
         String sourceCode = "public class ErrorClass {\n" +
@@ -90,15 +80,17 @@ void testCompileFromString_CompilationError() {
                 "    }\n" +
                 "}";
 
+        // Just verify compilation fails and no class file is created
         boolean result = compilerUtil.compileFromString(className, sourceCode);
+        assertFalse(result, "Compilation should fail due to syntax error");
 
-        assertFalse(result, "Compilation should fail");
-        assertTrue(outputCaptor.toString().contains("';' expected"),
-                "Diagnostic should mention missing semicolon");
+        // Check that no class file was created
+        Path classFile = compilerUtil.getOutputDirectory().resolve(className + ".class");
+        assertFalse(Files.exists(classFile), "No class file should be created for failed compilation");
     }
 
     @Test
-    void testCompileFile_Success() throws Exception {
+    void given_javaSourceFile_when_compiled_then_compilationSucceeds() throws Exception {
         // Create a temporary Java file
         String className = "FileTest";
         String sourceCode = "public class FileTest {\n" +
@@ -120,7 +112,7 @@ void testCompileFile_Success() throws Exception {
     }
 
     @Test
-    void testRunClass() throws Exception {
+    void given_compiledClass_when_runWithArguments_then_outputsExpectedResult() throws Exception {
         // Compile a simple class
         String className = "Runner";
         String sourceCode = "public class Runner {\n" +
@@ -132,23 +124,21 @@ void testRunClass() throws Exception {
         boolean result = compilerUtil.compileFromString(className, sourceCode);
         assertTrue(result, "Compilation should succeed");
 
-        // Clear the output capture
-        outputCaptor.reset();
-
-        // Run the compiled class
-        compilerUtil.runClass(className, "arg1", "arg2");
+        // Use system-lambda to capture the output
+        String output = tapSystemOut(() -> {
+            compilerUtil.runClass(className, "arg1", "arg2");
+        });
 
         // Check the output
-        assertEquals("Running: arg1, arg2", outputCaptor.toString().trim());
+        assertEquals("Running: arg1, arg2", output.trim());
     }
 
     @Test
-    void testCompileFile_FileNotExists() {
+    void when_compilingNonExistentFile_then_throwsIllegalArgumentException() {
         Path nonExistentFile = tempDir.resolve("NonExistent.java");
 
         assertThrows(IllegalArgumentException.class, () -> {
             compilerUtil.compileFile(nonExistentFile);
         });
     }
-
-}
+}