BAEL-9201: Count files in directory (#18436)

* initial commit

* Remove unnecessary code and dependencies

* Rename file to end with *UnitTest

Author: LeoHelfferich

core-java-modules/core-java-23/src/main/java/com/baeldung/javafeatures/FindFolder.java

@@ -0,0 +1,97 @@
+package com.baeldung.javafeatures;
+
+import static java.io.IO.println;
+
+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.Arrays;
+import java.util.Optional;
+import java.util.function.Function;
+import java.util.stream.Stream;
+
+public class FindFolder {
+
+    public static long numberOfFilesIn_classic(String path) {
+        File currentFile = new File(path);
+        File[] filesOrNull = currentFile.listFiles();
+        long currentFileNumber = currentFile.isFile() ? 1 : 0;
+
+        if (filesOrNull == null) {
+            return currentFileNumber;
+        }
+
+        for (File file : filesOrNull) {
+            if (file.isDirectory()) {
+                currentFileNumber += numberOfFilesIn_classic(file.getAbsolutePath());
+            } else if (file.isFile()) {
+                currentFileNumber += 1;
+            }
+        }
+
+        return currentFileNumber;
+    }
+
+    public static long numberOfFilesIn_Stream(String path) {
+        File currentFile = new File(path);
+        File[] filesOrNull = currentFile.listFiles();
+        long currentFileNumber = currentFile.isFile() ? 1 : 0;
+
+        if (filesOrNull == null) {
+            return currentFileNumber;
+        }
+
+        return currentFileNumber + Arrays.stream(filesOrNull)
+            .mapToLong(FindFolder::filesInside)
+            .sum();
+    }
+
+    private static long filesInside(File it) {
+        if (it.isFile()) {
+            return 1;
+        } else if (it.isDirectory()) {
+            return numberOfFilesIn_Stream(it.getAbsolutePath());
+        } else {
+            return 0;
+        }
+    }
+
+    public static long numberOfFilesIn_Walk(String path) {
+        Path dir = Path.of(path);
+        try (Stream<Path> stream = Files.walk(dir)) {
+            return stream.parallel()
+                .map(getFileOrEmpty())
+                .flatMap(Optional::stream)
+                .filter(it -> !it.isDirectory())
+                .count();
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private static Function<Path, Optional<File>> getFileOrEmpty() {
+        return it -> {
+            try {
+                return Optional.of(it.toFile());
+            } catch (UnsupportedOperationException e) {
+                println(e);
+                return Optional.empty();
+            }
+        };
+    }
+
+    public static long numberOfFilesIn_NIO(String path) {
+        try (Stream<Path> stream = Files.find(
+            Paths.get(path),
+            Integer.MAX_VALUE,
+            (__, attr) -> attr.isRegularFile())
+        ) {
+            return stream.count();
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}
+

core-java-modules/core-java-23/src/test/java/com/baeldung/javafeatures/NumberOfFilesUnitTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.javafeatures;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.function.Function;
+import java.util.stream.Stream;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+public class NumberOfFilesUnitTest {
+
+    private final String resourcePath = this.getClass()
+        .getResource("/filesToBeFound")
+        .getPath();
+
+    @ParameterizedTest
+    @MethodSource("functionsUnderTest")
+    void shouldReturnNumberOfAllFilesInsidePath(Function<String, Long> functionUnderTest) {
+        long expectedCount = 5;
+
+        long result = functionUnderTest.apply(resourcePath);
+
+        assertThat(result).isEqualTo(expectedCount);
+    }
+
+    private static Stream<Arguments> functionsUnderTest() {
+        return Stream.<Function<String, Long>> of(
+            FindFolder::numberOfFilesIn_Walk,
+                FindFolder::numberOfFilesIn_classic,
+                FindFolder::numberOfFilesIn_Stream,
+                FindFolder::numberOfFilesIn_NIO
+            )
+            .map(Arguments::of);
+    }
+}