BAEL-4394: Line at a given number tests

core-java-modules/core-java-io-3/src/test/java/com/baeldung/linenumber/LineAtGivenNumberTest.java

@@ -0,0 +1,88 @@
+package com.baeldung.linenumber;
+
+import org.apache.commons.io.FileUtils;
+import org.apache.commons.io.IOUtils;
+import org.junit.Test;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.List;
+import java.util.Scanner;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertEquals;
+
+public class LineAtGivenNumberTest {
+
+    private static final String FILE_PATH = "src/test/resources/linesInput.txt";
+
+    @Test
+    public void givenFile_whenUsingBufferedReader_thenExtractedLineIsCorrect() throws IOException {
+        try (BufferedReader br = Files.newBufferedReader(Paths.get(FILE_PATH))) {
+            for (int i = 0; i < 3; i++) {
+                br.readLine();
+            }
+
+            String extractedLine = br.readLine();
+            String expectedLine = "Line 4";
+            assertEquals(expectedLine, extractedLine);
+        }
+    }
+
+    @Test
+    public void givenFile_whenUsingScanner_thenExtractedLineIsCorrect() throws IOException {
+        try (Scanner scanner = new Scanner(new File(FILE_PATH))) {
+            for (int i = 0; i < 3; i++) {
+                scanner.nextLine();
+            }
+
+            String extractedLine = scanner.nextLine();
+            String expectedLine = "Line 4";
+            assertEquals(expectedLine, extractedLine);
+        }
+    }
+
+    @Test
+    public void givenSmallFile_whenUsingFilesAPI_thenExtractedLineIsCorrect() throws IOException {
+        String extractedLine = Files.readAllLines(Paths.get(FILE_PATH)).get(4);
+        String expectedLine = "Line 5";
+
+        assertEquals(expectedLine, extractedLine);
+    }
+
+    @Test
+    public void givenLargeFile_whenUsingFilesAPI_thenExtractedLineIsCorrect() throws IOException {
+        try (Stream<String> lines = Files.lines(Paths.get(FILE_PATH))) {
+            String extractedLine = lines.skip(4).findFirst().get();
+            String expectedLine = "Line 5";
+
+            assertEquals(expectedLine, extractedLine);
+        }
+    }
+
+    @Test
+    public void givenFile_whenUsingFIleUtils_thenExtractedLineIsCorrect() throws IOException {
+        ClassLoader classLoader = getClass().getClassLoader();
+        File file = new File(classLoader.getResource("linesInput.txt").getFile());
+
+        List<String> lines = FileUtils.readLines(file, "UTF-8");
+
+        String extractedLine = lines.get(0);
+        String expectedLine = "Line 1";
+        assertEquals(expectedLine, extractedLine);
+    }
+
+    @Test
+    public void givenFile_whenUsingIOUtils_thenExtractedLineIsCorrect() throws IOException {
+        String fileContent = IOUtils.toString(new FileInputStream(FILE_PATH), StandardCharsets.UTF_8);
+
+        String extractedLine = fileContent.split(System.lineSeparator())[0];
+        String expectedLine = "Line 1";
+        assertEquals(expectedLine, extractedLine);
+    }
+}

core-java-modules/core-java-io-3/src/test/resources/linesInput.txt

@@ -0,0 +1,5 @@
+Line 1
+Line 2
+Line 3
+Line 4
+Line 5