[BAEL-2032] Operate on an item in a Stream then remove it (#4955)

* [BAEL-2032] Operate on an item in a Stream then remove it

* [BAEL-2032] Refactored unit test

* [BAEL-2032] Added a new test for filter and used logger

core-java-collections/src/test/java/com/baeldung/collection/StreamOperateAndRemoveUnitTest.java

@@ -0,0 +1,78 @@
+package com.baeldung.collection;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class StreamOperateAndRemoveUnitTest {
+
+    private List<Item> itemList;
+
+    @Before
+    public void setup() {
+
+        itemList = new ArrayList<>();
+        for (int i = 0; i < 10; i++) {
+            itemList.add(new Item(i));
+        }
+    }
+
+    @Test
+    public void givenAListOf10Items_whenFilteredForQualifiedItems_thenFilteredListContains5Items() {
+
+        final List<Item> filteredList = itemList.stream().filter(item -> item.isQualified())
+            .collect(Collectors.toList());
+
+        Assert.assertEquals(5, filteredList.size());
+    }
+
+    @Test
+    public void givenAListOf10Items_whenOperateAndRemoveQualifiedItemsUsingRemoveIf_thenListContains5Items() {
+
+        itemList.stream().filter(item -> item.isQualified()).forEach(item -> item.operate());
+        itemList.removeIf(item -> item.isQualified());
+
+        Assert.assertEquals(5, itemList.size());
+    }
+
+    @Test
+    public void givenAListOf10Items_whenOperateAndRemoveQualifiedItemsUsingRemoveAll_thenListContains5Items() {
+
+        final List<Item> operatedList = new ArrayList<>();
+        itemList.stream().filter(item -> item.isQualified()).forEach(item -> {
+            item.operate();
+            operatedList.add(item);
+        });
+        itemList.removeAll(operatedList);
+
+        Assert.assertEquals(5, itemList.size());
+    }
+
+    class Item {
+
+        private final Logger logger = LoggerFactory.getLogger(this.getClass().getName());
+
+        private final int value;
+
+        public Item(final int value) {
+
+            this.value = value;
+        }
+
+        public boolean isQualified() {
+
+            return value % 2 == 0;
+        }
+
+        public void operate() {
+
+            logger.info("Even Number: " + this.value);
+        }
+    }
+}