Integrate forEach and stream changes to test, removing non-test class. (#1529)

* article Bael-667 initial commit.

* Switch to use logging framework for output.

core-java/src/test/java/com/baeldung/list/flattennestedlist/FlattenNestedListTest.java

@@ -1,6 +1,8 @@
 package com.baeldung.list.flattennestedlist;
 
-import org.junit.Test;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -8,45 +10,60 @@ import java.util.Collection;
 import java.util.List;
 import java.util.stream.Collectors;
 
-import static org.junit.Assert.assertNotNull;
+import org.junit.After;
-import static org.junit.Assert.assertTrue;
+import org.junit.Before;
+import org.junit.Test;
 
 public class FlattenNestedListTest {
+    private List<List<String>> lol = new ArrayList<>();
+    List<String> ls1 = Arrays.asList("one:one", "one:two", "one:three");
+    List<String> ls2 = Arrays.asList("two:one", "two:two", "two:three");
+    List<String> ls3 = Arrays.asList("three:one", "three:two", "three:three");
 
-    @Test
+    @Before
-    public void givenListOfListOfString_flattenNestedList1() {
+    public void setup() {
-        // given
+        lol.addAll(Arrays.asList(ls1, ls2, ls3));
-        List<String> ls1 = Arrays.asList("one:one", "one:two", "one:three");
+    }
-        List<String> ls2 = Arrays.asList("two:one", "two:two", "two:three");
-        List<String> ls3 = Arrays.asList("three:one", "three:two", "three:three");
 
-        List<List<String>> list = Arrays.asList(ls1, ls2, ls3);
+    @After
-
+    public void tearDown() {
-        // when
+        lol = null;
-        List<String> ls = flattenListOfListsImperatively(list);
-
-        // then
-        assertNotNull(ls);
-        assertTrue(ls.size() == 9);
-        //TODO content assertion
     }
 
     @Test
-    public void givenListOfListOfString_flattenNestedList2() {
+    public void givenString_flattenNestedList1() {
-        // given
+        List<String> ls = flattenListOfListsImperatively(lol);
-        List<String> ls1 = Arrays.asList("one:one", "one:two", "one:three");
-        List<String> ls2 = Arrays.asList("two:one", "two:two", "two:three");
-        List<String> ls3 = Arrays.asList("three:one", "three:two", "three:three");
 
-        List<List<String>> list = Arrays.asList(ls1, ls2, ls3);
-
-        // when
-        List<String> ls = flattenListOfListsStream(list);
-
-        // then
         assertNotNull(ls);
         assertTrue(ls.size() == 9);
-        //TODO content assertion
+        // assert content
+        assertEquals(ls.get(0), "one:one");
+        assertEquals(ls.get(1), "one:two");
+        assertEquals(ls.get(2), "one:three");
+        assertEquals(ls.get(3), "two:one");
+        assertEquals(ls.get(4), "two:two");
+        assertEquals(ls.get(5), "two:three");
+        assertEquals(ls.get(6), "three:one");
+        assertEquals(ls.get(7), "three:two");
+        assertEquals(ls.get(8), "three:three");
+    }
+
+    @Test
+    public void givenString_flattenNestedList2() {
+        List<String> ls = flattenListOfListsStream(lol);
+
+        assertNotNull(ls);
+        assertTrue(ls.size() == 9);
+        // assert content
+        assertEquals(ls.get(0), "one:one");
+        assertEquals(ls.get(1), "one:two");
+        assertEquals(ls.get(2), "one:three");
+        assertEquals(ls.get(3), "two:one");
+        assertEquals(ls.get(4), "two:two");
+        assertEquals(ls.get(5), "two:three");
+        assertEquals(ls.get(6), "three:one");
+        assertEquals(ls.get(7), "three:two");
+        assertEquals(ls.get(8), "three:three");
     }
 
     public <T> List<T> flattenListOfListsImperatively(List<List<T>> list) {
@@ -56,9 +73,6 @@ public class FlattenNestedListTest {
     }
 
     public <T> List<T> flattenListOfListsStream(List<List<T>> list) {
-        return list.stream()
+        return list.stream().flatMap(Collection::stream).collect(Collectors.toList());
-          .flatMap(Collection::stream)
-          .collect(Collectors.toList());
     }
-
 }