Merge pull request #16290 from hajk1/BAEL-7497

BAEL-7497 iterator Vs foreach()

core-java-modules/core-java-collections-6/README.md

@@ -3,3 +3,5 @@
 ## Core Java Collections Cookbooks and Examples
 
 ### Relevant Articles:
+
+- More articles: [[<-- prev]](/core-java-modules/core-java-collections-5)

core-java-modules/core-java-collections-6/src/test/java/com/baeldung/iteratorvsforeach/IteratorVsForeachUnitTest.java

@@ -0,0 +1,64 @@
+package com.baeldung.iteratorvsforeach;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertIterableEquals;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.stream.Stream;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+class IteratorVsForeachUnitTest {
+
+    private static Stream<Arguments> listProvider() {
+        return Stream.of(Arguments.of(List.of("String1", "String2", "unwanted"), List.of("String1", "String2")));
+    }
+
+    @Test
+    public void givenEmptyCollection_whenUsingForEach_thenNoElementsAreIterated() {
+        List<String> names = Collections.emptyList();
+        StringBuilder stringBuilder = new StringBuilder();
+        names.forEach(stringBuilder::append);
+        assertEquals("", stringBuilder.toString());
+    }
+
+    @ParameterizedTest
+    @MethodSource("listProvider")
+    public void givenCollectionWithElements_whenRemovingElementDuringForEachIteration_thenElementIsRemoved(List<String> input, List<String> expected) {
+        List<String> mutableList = new ArrayList<>(input);
+        // Separate collection for items to be removed
+        List<String> toRemove = new ArrayList<>();
+
+        // Using forEach to identify items to remove
+        input.forEach(item -> {
+            if (item.equals("unwanted")) {
+                toRemove.add(item);
+            }
+        });
+
+        // Removing the identified items from the original list
+        mutableList.removeAll(toRemove);
+        assertIterableEquals(expected, mutableList);
+    }
+
+    @ParameterizedTest
+    @MethodSource("listProvider")
+    public void givenCollectionWithElements_whenRemovingElementDuringIteratorIteration_thenElementIsRemoved(List<String> input, List<String> expected) {
+        List<String> mutableList = new ArrayList<>(input);
+        Iterator<String> it = mutableList.iterator();
+        while (it.hasNext()) {
+            String item = it.next();
+            if (item.equals("unwanted")) {
+                it.remove(); // Safely remove item
+            }
+        }
+        assertIterableEquals(expected, mutableList);
+    }
+
+}