BAEL-725: How to iterate over a map? (#1959)

* BAEL-725: How to iterate over a map? * Changed the name of the tests in MapIterationTest.java
2017-06-07 13:22:28 -07:00
parent 0529906f47
commit 4453358bfb
2 changed files with 127 additions and 0 deletions
@@ -0,0 +1,58 @@
+package com.baeldung.map.iteration;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+
+public class MapIteration {
+
+    public List<String> iterateUsingEntrySet(Map<String, Integer> map) {
+        List<String> mapKeyValueList = new ArrayList<>();
+        for (Map.Entry<String, Integer> entry : map.entrySet()) {
+            mapKeyValueList.add(entry.getKey() + ":" + entry.getValue());
+        }
+        return mapKeyValueList;
+    }
+
+    public List<String> iterateUsingLambda(Map<String, Integer> map) {
+        List<String> mapKeyValueList = new ArrayList<>();
+        map.forEach((k, v) -> mapKeyValueList.add(k + ":" + v));
+        return mapKeyValueList;
+    }
+
+    public List<String> iterateUsingIteratorAndEntry(Map<String, Integer> map) {
+        ArrayList<String> mapKeyValueList = new ArrayList<>();
+        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 List<String> iterateUsingKeySetAndForeach(Map<String, Integer> map) {
+        List<String> mapKeyValueList = new ArrayList<>();
+        for (String key : map.keySet()) {
+            mapKeyValueList.add(key + ":" + map.get(key));
+        }
+        return mapKeyValueList;
+    }
+
+    public List<String> iterateUsingStreamAPI(Map<String, Integer> map) {
+        ArrayList<String> mapKeyValueList = new ArrayList<>();
+        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<>();
+        for (String key : map.keySet()) {
+            mapKeyList.add(key);
+        }
+        return mapKeyList;
+    }
+
+}