poprawiona klasa oraz testy, rozpoczęcie pracy nad drugą klasą

KonwersjaLiter2/src/main/java/pl/dmcs/DirConverter.java

@@ -1,5 +1,25 @@
 package pl.dmcs;
+import java.io.File;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import java.io.IOException;
 
 public class DirConverter {
+    public void convertDir(String directoryPath, String fileExtension) throws IOException {
+        try (Stream<Path> filePathStream = Files.walk(Paths.get(directoryPath))) {
+            List<Path> files = filePathStream.filter(Files::isRegularFile).filter(path -> path.getFileName().toString().endsWith(fileExtension)).collect(Collectors.toList());
+
+            for (Path file : files) {
+                List<String> lines = Files.readAllLines(file);
+                List<String> upperCasedLines = lines.stream().map(String::toUpperCase).collect(Collectors.toList());
+                Files.write(file, upperCasedLines);
+                }
+            }
+        }
+    }
 
-}

KonwersjaLiter2/src/test/java/pl/dmcs/DirConverterTest.java

@@ -0,0 +1,26 @@
+package pl.dmcs;
+
+import org.junit.jupiter.api.BeforeEach;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+
+public class DirConverterTest {
+    private static final String TEST_DIR = "target/test-classes/";
+
+    private static final String FILE_EXTENSION = ".txt";
+
+    @BeforeEach
+    void setUp() throws IOException {
+        Files.createDirectory(Paths.get(TEST_DIR));
+
+        Files.write(Paths.get(TEST_DIR, "file1.txt"), "hello world".getBytes());
+        Files.write(Paths.get(TEST_DIR, "file2.txt"), "hello world 2".getBytes());
+        Files.write(Paths.get(TEST_DIR, "file3.txt"), "hello world 3".getBytes());
+    }
+
+
+}
+