This commit is related to BAEL-6463 (#16753)

This commit aims to add a test class ClearScannerBufferUnitTest.

Author: BenHelmyBen

core-java-modules/core-java-io-6/src/test/java/com/baeldung/clearscannerbuffer/ClearScannerBufferUnitTest.java

@@ -0,0 +1,68 @@
+package clearscannerbuffer;
+
+
+import org.junit.Test;
+
+import java.io.ByteArrayInputStream;
+import java.util.Scanner;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertEquals;
+
+public class ClearScannerBufferUnitTest {
+    Scanner scanner = new Scanner("123\nHello World");
+
+    @Test
+    public void givenInput_whenUsingNextLineWithHasNextLine_thenBufferCleared() {
+
+        int number = scanner.nextInt();
+        if (scanner.hasNextLine()) {
+            scanner.nextLine();
+        }
+        String text = scanner.nextLine();
+
+        assertEquals(123, number);
+        assertEquals("Hello World", text);
+    }
+
+    @Test
+    public void givenInput_whenUsingReset_thenBufferCleared() {
+        String input = "123\nHello World";
+        ByteArrayInputStream inputStream = new ByteArrayInputStream(input.getBytes());
+        Scanner scanner = new Scanner(inputStream);
+
+        int number = scanner.nextInt();
+
+        inputStream.reset();
+        scanner = new Scanner(inputStream);
+
+        int newNumber = scanner.nextInt();
+
+        scanner.nextLine();
+
+        String text = scanner.nextLine();
+
+        assertEquals(123, number);
+        assertEquals(123, newNumber);
+        assertEquals("Hello World", text);
+    }
+
+    @Test
+    public void givenInput_whenUsingStreamAPI_thenBufferCleared() {
+        Scanner scanner = new Scanner("123\nline1\nline2\nexit");
+
+        int number = scanner.nextInt();
+
+        scanner.nextLine();
+
+        String lines = Stream.generate(scanner::nextLine)
+                .takeWhile(line -> !line.equalsIgnoreCase("exit"))
+                .collect(Collectors.joining(System.lineSeparator()));
+
+        String expectedLines = "line1" + System.lineSeparator() + "line2";
+
+        assertEquals(123, number);
+        assertEquals(expectedLines, lines);
+    }
+}