BAEL-5162 : HashMap Entry Removal (#11276)

core-java-modules/core-java-collections-maps-3/src/main/java/com/baeldung/map/hashmap/entryremoval/RemoveEntryApplication.java

@@ -0,0 +1,74 @@
+package com.baeldung.map.hashmap.entryremoval;
+
+import java.util.ConcurrentModificationException;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map.Entry;
+import java.util.concurrent.ConcurrentHashMap;
+
+public class RemoveEntryApplication {
+
+    public static void main(String[] args) {
+
+        HashMap<String, String> foodItemTypeMap = new HashMap<>();
+        foodItemTypeMap.put("Apple", "Fruit");
+        foodItemTypeMap.put("Grape", "Fruit");
+        foodItemTypeMap.put("Mango", "Fruit");
+        foodItemTypeMap.put("Carrot", "Vegetable");
+        foodItemTypeMap.put("Potato", "Vegetable");
+        foodItemTypeMap.put("Spinach", "Vegetable");
+        // Current Map Status: {Potato=Vegetable, Apple=Fruit, Carrot=Vegetable, Grape=Fruit, Mango=Fruit, Spinach=Vegetable}
+
+        foodItemTypeMap.remove("Apple");
+        // Current Map Status: {Potato=Vegetable, Carrot=Vegetable, Grape=Fruit, Mango=Fruit, Spinach=Vegetable}
+
+        foodItemTypeMap.remove("Grape", "Vegetable");
+        // Current Map Status: {Potato=Vegetable, Carrot=Vegetable, Grape=Fruit, Mango=Fruit, Spinach=Vegetable}
+
+        try {
+            for (Entry<String, String> item : foodItemTypeMap.entrySet()) {
+                if (item.getKey()
+                    .equals("Potato")) {
+                    foodItemTypeMap.remove(item.getKey());
+                }
+            }
+        } catch (ConcurrentModificationException e) {
+            System.out.println("Exception occured while updating map: " + e.toString());
+        }
+
+        foodItemTypeMap.entrySet()
+            .removeIf(entry -> entry.getKey()
+                .equals("Grape"));
+        // Current Map Status: {Carrot=Vegetable, Mango=Fruit, Spinach=Vegetable}
+
+        Iterator<Entry<String, String>> iterator = foodItemTypeMap.entrySet()
+            .iterator();
+        while (iterator.hasNext()) {
+            if (iterator.next()
+                .getKey()
+                .equals("Carrot"))
+                iterator.remove();
+        }
+        // Current Map Status: {Mango=Fruit, Spinach=Vegetable}
+
+        // Use ConcurrentHashMap
+        ConcurrentHashMap<String, String> foodItemTypeConcMap = new ConcurrentHashMap<>();
+        foodItemTypeConcMap.put("Apple", "Fruit");
+        foodItemTypeConcMap.put("Grape", "Fruit");
+        foodItemTypeConcMap.put("Mango", "Fruit");
+        foodItemTypeConcMap.put("Carrot", "Vegetable");
+        foodItemTypeConcMap.put("Potato", "Vegetable");
+        foodItemTypeConcMap.put("Spinach", "Vegetable");
+
+        for (Entry<String, String> item : foodItemTypeConcMap.entrySet()) {
+            if (item.getKey() != null && item.getKey()
+                .equals("Potato")) {
+                foodItemTypeConcMap.remove(item.getKey());
+            }
+        }
+
+        // foodItemTypeConcMap : {Apple=Fruit, Carrot=Vegetable, Grape=Fruit, Mango=Fruit, Spinach=Vegetable}
+
+    }
+
+}