map with timestamp done

Author: rampatra

src/main/java/com/rampatra/java8/FlatMapInStreams.java

@@ -11,7 +11,10 @@
 public class FlatMapInStreams {
 
     public static long countTotalIngredientsInAllDishes(List<Dish> dishes) {
-        return dishes.stream().map(Dish::getIngredients).flatMap(List::stream).count();
+        return dishes.stream()
+                .map(Dish::getIngredients)
+                .flatMap(List::stream)
+                .count();
     }
 
     public static void main(String[] args) {
@@ -21,7 +24,7 @@ public static void main(String[] args) {
         ingredients.add("haldi");
         List<Dish> dishes = Arrays.asList(
                 new Dish("biriyani", 600, ingredients),
-                new Dish("biriyani", 600, new ArrayList<>()));
+                new Dish("pulao", 600, new ArrayList<>()));
         // to show whether empty List is counted in flatMap
         System.out.println(countTotalIngredientsInAllDishes(dishes));
     }

src/main/java/com/rampatra/misc/MapWithTimestamp.java

@@ -0,0 +1,50 @@
+package com.rampatra.misc;
+
+import java.util.Date;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * @author rampatra
+ * @since 2019-05-15
+ */
+public class MapWithTimestamp<K, V> {
+
+    private final Map<K, Map<Long, V>> map = new HashMap<>();
+
+    public V get(K key, Long timestamp) {
+        Map<Long, V> entry = map.get(key);
+
+        return entry != null ? entry.get(timestamp) : null;
+    }
+
+    public void put(K key, Long timestamp, V value) {
+        Map<Long, V> entry = map.get(key);
+
+        if (entry == null) {
+            map.put(key, new HashMap<Long, V>() {{
+                put(timestamp, value);
+            }});
+        } else {
+            entry.put(timestamp, value);
+        }
+    }
+
+    public static void main(String[] args) throws Exception {
+        MapWithTimestamp<Integer, Integer> mapWithTimestamp = new MapWithTimestamp<>();
+        long timestamp1;
+        long timestamp2;
+        long timestamp3;
+
+        mapWithTimestamp.put(1, timestamp1 = new Date().getTime(), 10_0);
+        mapWithTimestamp.put(2, timestamp2 = new Date().getTime(), 20_0);
+        Thread.sleep(100);
+        mapWithTimestamp.put(2, new Date().getTime(), 20_1);
+        Thread.sleep(100);
+        mapWithTimestamp.put(2, new Date().getTime(), 20_2);
+        mapWithTimestamp.put(3, timestamp3 = new Date().getTime(), 30_0);
+        System.out.println(mapWithTimestamp.get(2, timestamp2));
+        System.out.println(mapWithTimestamp.get(3, timestamp2));
+        System.out.println(mapWithTimestamp.get(3, timestamp3));
+    }
+}