[BAEL-6051_intListToStrList] convert List<Integer> to List<String> (#13169)

core-java-modules/core-java-collections-conversions-2/src/test/java/com/baeldung/intlisttostrlist/IntListToStringListUnitTest.java

@@ -0,0 +1,40 @@
+package com.baeldung.intlisttostrlist;
+
+
+import com.google.common.base.Functions;
+import com.google.common.collect.Lists;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class IntListToStringListUnitTest {
+    private final static List<Integer> INTEGER_LIST = Arrays.asList(1, 2, 3, 4, 5, 6, 7);
+    private final static List<String> EXPECTED_LIST = Arrays.asList("1", "2", "3", "4", "5", "6", "7");
+
+
+    @Test
+    void givenAnIntegerList_whenUsingStreamMap_shouldGetExpectedStringList() {
+        List<String> result = INTEGER_LIST.stream().map(i -> i.toString()).collect(Collectors.toList());
+        assertEquals(EXPECTED_LIST, result);
+    }
+
+    @Test
+    void givenAnIntegerList_whenUsingGuava_shouldGetExpectedStringList() {
+        List<String> result = Lists.transform(INTEGER_LIST, Functions.toStringFunction());
+        assertEquals(EXPECTED_LIST, result);
+    }
+
+    @Test
+    void givenAnIntegerList_whenUsingLoop_shouldGetExpectedStringList() {
+        List<String> result = new ArrayList<>();
+        for (Integer i : INTEGER_LIST) {
+            result.add(i.toString());
+        }
+        assertEquals(EXPECTED_LIST, result);
+    }
+}