added util class for finding all classes in the current class path

src/de/christianleberfinger/melodies2go/utils/Classes.java

@@ -0,0 +1,89 @@
+package de.christianleberfinger.melodies2go.utils;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.HashSet;
+import java.util.LinkedHashSet;
+import java.util.Set;
+import java.util.jar.JarEntry;
+import java.util.jar.JarFile;
+import java.util.stream.Stream;
+
+public class Classes {
+
+    public static Set<String> findAllClassNamesInClassPath() {
+        Set<Path> classPathElements = getClassPaths();
+        Set<String> classes = new LinkedHashSet<>();
+        classPathElements.forEach(classPathElement -> addAllClassesFrom(classPathElement, classes));
+        return classes;
+    }
+
+    protected static void addAllClassesFrom(Path p, Set<String> classes) {
+        if (Files.isDirectory(p)) {
+            addClassNamesFromDir(p, classes);
+        } else {
+            if (isClassFile(p)) {
+                String className = classNameFromFilePath(p.toString());
+                classes.add(className);
+            } else {
+                addClassNamesFromJar(p, classes);
+            }
+        }
+    }
+
+    private static void addClassNamesFromDir(Path dir, Set<String> classNames) {
+        try (Stream<Path> children = Files.walk(dir)) {
+            children.filter(Classes::isClassFile)
+                    .forEach(child -> {
+                        Path relativePath = dir.relativize(child);
+                        String className = classNameFromFilePath(relativePath.toString());
+                        classNames.add(className);
+                    });
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private static void addClassNamesFromJar(Path p, Set<String> classes) {
+        try (JarFile jar = new JarFile(p.toFile())) {
+            jar.stream()
+                    .filter(Classes::isClassEntry)
+                    .map(JarEntry::getName)
+                    .map(Classes::classNameFromFilePath)
+                    .forEach(classes::add);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    protected static String classNameFromFilePath(String path) {
+        path = path.substring(0, path.lastIndexOf(".class"));
+        return path.replaceAll("/", ".");
+    }
+
+    protected static Set<Path> getClassPaths() {
+        String classpathProp = System.getProperty("java.class.path");
+        String[] classPathElements = classpathProp.split(File.pathSeparator);
+        Set<Path> classPaths = new HashSet<>(classPathElements.length);
+        for (String element : classPathElements) {
+            Path path = Paths.get(element);
+            if (Files.exists(path)) {
+                classPaths.add(path);
+            }
+        }
+
+        return classPaths;
+    }
+
+    private static boolean isClassEntry(JarEntry entry) {
+        return entry.getName().endsWith(".class");
+    }
+
+    private static boolean isClassFile(Path p) {
+        return Files.isRegularFile(p) &&
+                p.getFileName().toString().endsWith(".class");
+    }
+}

test/de/christianleberfinger/melodies2go/utils/ClassesTest.java

@@ -0,0 +1,33 @@
+package de.christianleberfinger.melodies2go.utils;
+
+import de.christianleberfinger.melodies2go.M3UWriter;
+import org.junit.jupiter.api.Test;
+
+import java.nio.file.Path;
+import java.util.Set;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+
+public class ClassesTest {
+
+    @Test
+    public void getClassPaths() {
+        Set<Path> paths = Classes.getClassPaths();
+        assertNotNull(paths);
+        assertNotEquals(0, paths.size());
+    }
+
+    @Test
+    public void getClassNames() {
+        Set<String> classNames = Classes.findAllClassNamesInClassPath();
+        assertNotNull(classNames);
+        assertNotEquals(0, classNames.size());
+
+        assertTrue(classNames.contains(Object.class.getName()));
+        assertTrue(classNames.contains(M3UWriter.class.getName()));
+        assertTrue(classNames.contains(Classes.class.getName()));
+        assertFalse(classNames.contains(""));
+    }
+
+}