BAEL-6465: How to handle NoSuchElementException when reading a file through a Scanner ? (#13999)

core-java-modules/core-java-io-apis-2/src/main/java/com/baeldung/scanner/ScannerNoSuchElementException.java

@@ -0,0 +1,58 @@
+package com.baeldung.scanner;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.NoSuchElementException;
+import java.util.Scanner;
+
+public class ScannerNoSuchElementException {
+
+    public static String readFileV1(String pathname) throws IOException {
+        Path pathFile = Paths.get(pathname);
+        if (Files.notExists(pathFile)) {
+            return "";
+        }
+
+        try (Scanner scanner = new Scanner(pathFile)) {
+            return scanner.nextLine();
+        }
+    }
+
+    public static String readFileV2(String pathname) throws IOException {
+        Path pathFile = Paths.get(pathname);
+        if (Files.notExists(pathFile)) {
+            return "";
+        }
+
+        try (Scanner scanner = new Scanner(pathFile)) {
+            return scanner.hasNextLine() ? scanner.nextLine() : "";
+        }
+    }
+
+    public static String readFileV3(String pathname) throws IOException {
+        Path pathFile = Paths.get(pathname);
+        if (Files.notExists(pathFile) || Files.size(pathFile) == 0) {
+            return "";
+        }
+
+        try (Scanner scanner = new Scanner(pathFile)) {
+            return scanner.nextLine();
+        }
+    }
+
+    public static String readFileV4(String pathname) throws IOException {
+        Path pathFile = Paths.get(pathname);
+        if (Files.notExists(pathFile)) {
+            return "";
+        }
+
+        try (Scanner scanner = new Scanner(pathFile)) {
+            return scanner.nextLine();
+        } catch (NoSuchElementException exception) {
+            return "";
+        }
+    }
+
+}

core-java-modules/core-java-io-apis-2/src/test/java/com/baeldung/scanner/ScannerNoSuchElementExceptionUnitTest.java

@@ -0,0 +1,43 @@
+package com.baeldung.scanner;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.io.IOException;
+import java.util.NoSuchElementException;
+
+import org.junit.jupiter.api.Test;
+
+class ScannerNoSuchElementExceptionUnitTest {
+
+    @Test
+    void givenEmptyFile_whenUsingReadFileV1_thenThrowException() {
+        Exception exception = assertThrows(NoSuchElementException.class, () -> {
+            ScannerNoSuchElementException.readFileV1("src/test/resources/emptyFile.txt");
+        });
+
+        assertEquals("No line found", exception.getMessage());
+    }
+
+    @Test
+    void givenEmptyFile_whenUsingReadFileV2_thenSuccess() throws IOException {
+        String emptyLine = ScannerNoSuchElementException.readFileV2("src/test/resources/emptyFile.txt");
+
+        assertEquals("", emptyLine);
+    }
+
+    @Test
+    void givenEmptyFile_whenUsingReadFileV3_thenSuccess() throws IOException {
+        String emptyLine = ScannerNoSuchElementException.readFileV3("src/test/resources/emptyFile.txt");
+
+        assertEquals("", emptyLine);
+    }
+
+    @Test
+    void givenEmptyFile_whenUsingReadFileV4_thenSuccess() throws IOException {
+        String emptyLine = ScannerNoSuchElementException.readFileV4("src/test/resources/emptyFile.txt");
+
+        assertEquals("", emptyLine);
+    }
+
+}