From 9a2827f84e7782e806c45d58b7c0d4748b27d57a Mon Sep 17 00:00:00 2001
From: Pritam Banerjee <pritambanerjee999@gmail.com>
Date: Tue, 23 May 2017 03:32:06 -0700
Subject: [PATCH] BAEL-725: Map Iteration

---
 .../baeldung/map/iteration/MapIteration.java  | 57 ++++++++++++++++
 .../map/iteration/MapIterationTest.java       | 68 +++++++++++++++++++
 2 files changed, 125 insertions(+)
 create mode 100644 core-java/src/main/java/com/baeldung/map/iteration/MapIteration.java
 create mode 100644 core-java/src/test/java/com/baeldung/map/iteration/MapIterationTest.java

diff --git a/core-java/src/main/java/com/baeldung/map/iteration/MapIteration.java b/core-java/src/main/java/com/baeldung/map/iteration/MapIteration.java
new file mode 100644
index 0000000000..3b2a213aa0
--- /dev/null
+++ b/core-java/src/main/java/com/baeldung/map/iteration/MapIteration.java
@@ -0,0 +1,57 @@
+package com.baeldung.map.iteration;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.Map;
+
+public class MapIteration {
+
+    public ArrayList<String> iterateUsingEntrySet(Map<String, Integer> map) {
+        ArrayList<String> mapKeyValueList = new ArrayList<String>();
+        for (Map.Entry<String, Integer> entry : map.entrySet()) {
+            mapKeyValueList.add(entry.getKey() + ":" + entry.getValue());
+        }
+        return mapKeyValueList;
+    }
+
+    public ArrayList<String> iterateUsingLambda(Map<String, Integer> map) {
+        ArrayList<String> mapKeyValueList = new ArrayList<String>();
+        map.forEach((k, v) -> mapKeyValueList.add(k + ":" + v));
+        return mapKeyValueList;
+    }
+
+    public ArrayList<String> iterateUsingIteratorAndEntry(Map<String, Integer> map) {
+        ArrayList<String> mapKeyValueList = new ArrayList<String>();
+        Iterator<Map.Entry<String, Integer>> iterator = map.entrySet().iterator();
+
+        while (iterator.hasNext()) {
+            Map.Entry<String, Integer> pair = iterator.next();
+            mapKeyValueList.add(pair.getKey() + ":" + pair.getValue());
+        }
+
+        return mapKeyValueList;
+    }
+
+    public ArrayList<String> iterateUsingKeySetAndForeach(Map<String, Integer> map) {
+        ArrayList<String> mapKeyValueList = new ArrayList<String>();
+        for (String key : map.keySet()) {
+            mapKeyValueList.add(key + ":" + map.get(key));
+        }
+        return mapKeyValueList;
+    }
+
+    public ArrayList<String> iterateUsingStreamAPI(Map<String, Integer> map) {
+        ArrayList<String> mapKeyValueList = new ArrayList<String>();
+        map.entrySet().stream().forEach(e -> mapKeyValueList.add(e.getKey() + ":" + e.getValue()));
+        return mapKeyValueList;
+    }
+
+    public ArrayList<String> iterateKeys(Map<String, Integer> map) {
+        ArrayList<String> mapKeyList = new ArrayList<String>();
+        for (String key : map.keySet()) {
+            mapKeyList.add(key);
+        }
+        return mapKeyList;
+    }
+
+}
\ No newline at end of file
diff --git a/core-java/src/test/java/com/baeldung/map/iteration/MapIterationTest.java b/core-java/src/test/java/com/baeldung/map/iteration/MapIterationTest.java
new file mode 100644
index 0000000000..5953c118fd
--- /dev/null
+++ b/core-java/src/test/java/com/baeldung/map/iteration/MapIterationTest.java
@@ -0,0 +1,68 @@
+package com.baeldung.map.iteration;
+
+import static org.junit.Assert.assertTrue;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class MapIterationTest {
+
+    public static Map<String, Integer> testMap = new HashMap<String, Integer>();
+    public static String testString1 = "One:1";
+    public static String testString2 = "Two:2";
+    public static String testString3 = "Three:3";
+
+    @BeforeClass
+    public static void createTestData() {
+        testMap.put("One", 1);
+        testMap.put("Three", 3);
+        testMap.put("Two", 2);
+    }
+
+    @Test
+    public void iterateUsingEntrySet_test() {
+        MapIteration mapIteration = new MapIteration();
+        ArrayList<String> list = mapIteration.iterateUsingEntrySet(testMap);
+        assertTrue((list.contains(testString1)) && (list.contains(testString2)) && (list.contains(testString3)));
+    }
+
+    @Test
+    public void iterateUsingLambda_test() {
+        MapIteration mapIteration = new MapIteration();
+        ArrayList<String> list = mapIteration.iterateUsingLambda(testMap);
+        assertTrue((list.contains(testString1)) && (list.contains(testString2)) && (list.contains(testString3)));
+    }
+
+    @Test
+    public void iterateUsingIteratorAndEntry_test() {
+        MapIteration mapIteration = new MapIteration();
+        ArrayList<String> list = mapIteration.iterateUsingIteratorAndEntry(testMap);
+        assertTrue((list.contains(testString1)) && (list.contains(testString2)) && (list.contains(testString3)));
+    }
+
+    @Test
+    public void iterateUsingKeySetAndForeach_test() {
+        MapIteration mapIteration = new MapIteration();
+        ArrayList<String> list = mapIteration.iterateUsingKeySetAndForeach(testMap);
+        assertTrue((list.contains(testString1)) && (list.contains(testString2)) && (list.contains(testString3)));
+    }
+
+    @Test
+    public void iterateUsingStreamAPI_test() {
+        MapIteration mapIteration = new MapIteration();
+        ArrayList<String> list = mapIteration.iterateUsingStreamAPI(testMap);
+        assertTrue((list.contains(testString1)) && (list.contains(testString2)) && (list.contains(testString3)));
+    }
+
+    @Test
+    public void iterateKeys_test() {
+        MapIteration mapIteration = new MapIteration();
+        ArrayList<String> list = mapIteration.iterateKeys(testMap);
+        assertTrue((list.contains("One")) && (list.contains("Two")) && (list.contains("Three")));
+    }
+
+}