BAEL-1933 Added code examples and unit tests for creating symbolic links (#4608)

* BAEL-1933 Added code examples and unit tests for creating symbolic links

* Fixed PMD violation on unit test naming

* Fixed review comments

* Applied baeldung-eclipse formatter settings

core-java-io/src/main/java/com/baeldung/symlink/SymLinkExample.java

@@ -0,0 +1,54 @@
+package com.baeldung.symlink;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.DirectoryStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import static java.nio.file.StandardOpenOption.*;
+import java.util.stream.IntStream;
+
+public class SymLinkExample {
+
+    public void createSymbolicLink(Path link, Path target) throws IOException {
+        if (Files.exists(link)) {
+            Files.delete(link);
+        }
+        Files.createSymbolicLink(link, target);
+    }
+
+    public void createHardLink(Path link, Path target) throws IOException {
+        if (Files.exists(link)) {
+            Files.delete(link);
+        }
+        Files.createLink(link, target);
+    }
+
+    public Path createTextFile() throws IOException {
+        byte[] content = IntStream.range(0, 10000)
+            .mapToObj(i -> i + System.lineSeparator())
+            .reduce("", String::concat)
+            .getBytes(StandardCharsets.UTF_8);
+        Path filePath = Paths.get(".", "target_link.txt");
+        Files.write(filePath, content, CREATE, TRUNCATE_EXISTING);
+        return filePath;
+    }
+
+    public void printLinkFiles(Path path) throws IOException {
+        try (DirectoryStream<Path> stream = Files.newDirectoryStream(path)) {
+            for (Path file : stream) {
+                if (Files.isDirectory(file)) {
+                    printLinkFiles(file);
+                } else if (Files.isSymbolicLink(file)) {
+                    System.out.format("File link '%s' with target '%s'%n", file, Files.readSymbolicLink(file));
+                }
+            }
+        }
+    }
+
+    public static void main(String[] args) throws IOException {
+        new SymLinkExample().printLinkFiles(Paths.get("."));
+    }
+
+}

core-java-io/src/test/java/com/baeldung/symlink/SymLinkExampleUnitTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.symlink;
+
+import static org.junit.Assert.*;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+import org.junit.Test;
+
+public class SymLinkExampleUnitTest {
+
+    @Test
+    public void whenUsingFiles_thenCreateSymbolicLink() throws IOException {
+        SymLinkExample example = new SymLinkExample();
+        Path filePath = example.createTextFile();
+        Path linkPath = Paths.get(".", "symbolic_link.txt");
+        example.createSymbolicLink(linkPath, filePath);
+        assertTrue(Files.isSymbolicLink(linkPath));
+    }
+
+    @Test
+    public void whenUsingFiles_thenCreateHardLink() throws IOException {
+        SymLinkExample example = new SymLinkExample();
+        Path filePath = example.createTextFile();
+        Path linkPath = Paths.get(".", "hard_link.txt");
+        example.createHardLink(linkPath, filePath);
+        assertFalse(Files.isSymbolicLink(linkPath));
+        assertEquals(filePath.toFile()
+            .length(),
+            linkPath.toFile()
+                .length());
+    }
+
+}