[scanner-to-array] Saving Java Scanner Input to an Array (#13969)

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

@@ -0,0 +1,107 @@
+package com.baeldung.scanner;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Scanner;
+
+import org.junit.jupiter.api.Test;
+
+import com.google.common.collect.Lists;
+import com.google.common.collect.ObjectArrays;
+
+public class ScannerToArrayUnitTest {
+
+    @Test
+    void whenMultipleElementsInOneLine_thenGetExpectedArray() {
+        String input = "Java Kotlin Ruby Python Go\n";
+        String[] expected = new String[] { "Java", "Kotlin", "Ruby", "Python", "Go" };
+
+        // scanner.next()
+        Scanner scanner1 = new Scanner(input);
+        String[] result1 = new String[5];
+        int i = 0;
+        while (i < result1.length) {
+            result1[i] = scanner1.next();
+            i++;
+        }
+        assertArrayEquals(expected, result1);
+
+        //split()
+        Scanner scanner2 = new Scanner(input);
+        String[] result2 = scanner2.nextLine()
+          .split("\\s+");
+        assertArrayEquals(expected, result2);
+    }
+
+    @Test
+    void whenOneElementPerLine_thenGetExpectedArray() {
+        String input = new StringBuilder().append("Baeldung Java\n")
+          .append("Baeldung Kotlin\n")
+          .append("Baeldung Linux\n")
+          .toString();
+
+        String[] expected = new String[] { "Baeldung Java", "Baeldung Kotlin", "Baeldung Linux" };
+
+        String[] result = new String[3];
+        Scanner scanner = new Scanner(input);
+        int i = 0;
+        while (i < result.length) {
+            result[i] = scanner.nextLine();
+            i++;
+        }
+        assertArrayEquals(expected, result);
+    }
+
+    @Test
+    void whenOneElementPerLine_thenGetExpectedList() {
+        String input = new StringBuilder().append("Baeldung Java\n")
+          .append("Baeldung Kotlin\n")
+          .append("Baeldung Linux\n")
+          .toString();
+
+        List<String> expected = Lists.newArrayList("Baeldung Java", "Baeldung Kotlin", "Baeldung Linux");
+
+        List<String> result = new ArrayList<>();
+        Scanner scanner = new Scanner(input);
+        while (scanner.hasNextLine()) {
+            result.add(scanner.nextLine());
+        }
+        assertEquals(expected, result);
+    }
+
+    @Test
+    void whenEveryTokenIsAnElement_thenGetExpectedList() {
+        String input = new StringBuilder().append("Linux Windows MacOS\n")
+          .append("Java Kotlin Python Go\n")
+          .toString();
+
+        List<String> expected = Lists.newArrayList("Linux", "Windows", "MacOS", "Java", "Kotlin", "Python", "Go");
+        List<String> result = new ArrayList<>();
+        Scanner scanner = new Scanner(input);
+        while (scanner.hasNext()) {
+            result.add(scanner.next());
+        }
+        assertEquals(expected, result);
+    }
+
+    @Test
+    void whenEveryTokenIsAnElement_thenGetExpectedArray() {
+        String input = new StringBuilder().append("Linux Windows MacOS\n")
+          .append("Java Kotlin Python Go\n")
+          .toString();
+
+        String[] expected = new String[] { "Linux", "Windows", "MacOS", "Java", "Kotlin", "Python", "Go" };
+        String[] result = new String[] {};
+
+        Scanner scanner = new Scanner(input);
+        while (scanner.hasNextLine()) {
+            String[] lineInArray = scanner.nextLine()
+              .split("\\s+");
+            result = ObjectArrays.concat(result, lineInArray, String.class);
+        }
+        assertArrayEquals(expected, result);
+    }
+}