A hashmap inside of a hasmap print out

Question

I am trying to print out a hashmap that contains A character as the key and the value as another hashmap with Integer and Double I have this so far but isn't working.

HashMap<Character, Map<Integer, Double>> MapInsideOfAMap = calc.MapInAMap(abc);
 for (Entry<Character, Map<Integer, Double>> outer : MapInsideOfAMap.entrySet()) {
 System.out.println("Char: " + outer.getKey() + "\n");
 for (Map.Entry<Character, Map<Integer, Double> inner : MapInsideOfAMap.getValue().entrySet()) {
 System.out.println("int = " + inner.getKey() + ", double = " + inner.getValue());
 }
 }

• Betlista: What is MapInsideOfAMap, why you have Entry<Character, Map<Integer, Double>> (Double) in outer loop and Map.Entry<Integer, Integer> (Integer) in inner one?
• user6073886: There is no map method called getValue(). Change it to get(outer.getKey()). Also you suddenly switch from <Integer, Double> to <Integer, Integer> with your inner map. You need to be consistent.
• xMilos: stackoverflow.com/questions/2774608/… check
• 2345678: I've updated the code, sorry about the inconsistencies

Answer 1

Your code should be like this,

for (Entry<Character, Map<Integer, Double>> outer : MapInsideOfAMap.entrySet()) {
 System.out.println("Char: " + outer.getKey() + "\n");
 for (Entry<Integer, Double> inner : MapInsideOfAMap.get(outer.getKey()).entrySet()) {
 System.out.println("int = " + inner.getKey() + ", double = " + inner.getValue());
 }
 }

Okay, I understood what you were trying to do, since you already got Outer map entry, you don't have to again use outer map reference, you can directly do like this,

for (Entry<Character, Map<Integer, Double>> outer : MapInsideOfAMap.entrySet()) {
 System.out.println("Char: " + outer.getKey() + "\n");
 for (Entry<Integer, Double> inner : outer.getValue().entrySet()) {
 System.out.println("int = " + inner.getKey() + ", double = " + inner.getValue());
 }
 }

• osanger: `Valid soultion. but in my opionion you should avoid using MapInsideOfAMap.get(outer.getKey()).entrySet() ervery iteration. even if its O(1). But +1
• chaitanya89: @osanger yeah, correct, I was only trying to fix the error, I updated my answer.

Answer 2

Let's assume your map looks like this:

Map <Character, Map<Integer, Double>> MapInsideOfAMap = new HashMap();

then you can print your map like this:

for (Entry<Character, Map<Integer, Double>> outer : MapInsideOfAMap.entrySet()) {
 System.out.println("Char: " + outer.getKey() + "\n");
 HashMap<Integer, Double> innermap = MapInsideOfAMap.get(outer.getKey());
 for (Map.Entry<Integer, Double> innerEntry : innermap.entrySet()) {
 System.out.println("int = " + innerEntry.getKey() + ", double = " + innerEntry.getValue());
 }
}

Answer 3

If you need just to see map key/values, use System.out.println

Map AbstractMap.toString knows how to print itself in a nice and readable way.

Map<Character, Map<Integer, Double>> map = new HashMap<>();
map.put('A', new HashMap<>());
map.get('A').put(1, 0.01);
map.put('B', new HashMap<>());
map.get('B').put(2, 0.02);
System.out.println(map);

prints out this :

{A={1=0.01}, B={2=0.02}}

Answer 4

To simply print out the whole map of maps:

System.out.println(mapInsideOfAMap);

Now, if you want to iterate your outer and inner maps and print their key/value pairs you could use the Map.forEach method:

mapInsideOfAMap.forEach((outerKey, outerValue) -> {
 System.out.println("Char: " + outerKey + "\n");
 outerValue.forEach((innerKey, innerValue) -> 
 System.out.println("int = " + innerKey + ", double = " + innerValue));
});

• Pankaj Zanzane: Used Java8 Lambda expression
• fps: @Pankaj Yes, Map.forEach expects a BiConsumer that receives the key and the value, and this BiConsumer can be the target of a lambda expression to make the code more succint.

Answer 5

public static void main(String z[]) {
 Map<Character, Map<Integer, Double>> MapInsideOfAMap = getmapOfMap();
 for (Entry<Character, Map<Integer, Double>> outer : MapInsideOfAMap.entrySet()) {
 System.out.println("Char: " + outer.getKey() + "\n");
 Map<Integer, Double> mapInner = MapInsideOfAMap.get(outer.getKey());
 for (Map.Entry<Integer, Double> inner : mapInner.entrySet()) {
 System.out.println(inner.getKey() +":"+ mapInner.get(inner.getKey()));
 }
 }
}
private static Map getmapOfMap() {
 char[] chArr = {'a','b','c','d','e','f','g','h','i','j','k'};
 HashMap<Character, Map<Integer, Double>> mapInsideOfAMap = new HashMap<Character, Map<Integer, Double>>();
 for(char ch:chArr) {
 mapInsideOfAMap.put(ch, getInnterMap());
 }
 return mapInsideOfAMap;
}
private static Map getInnterMap() {
 Map<Integer, Double> map = new HashMap<>();
 for(int i=1000;i<1010;i++) {
 map.put(i, new Double(String.valueOf(i)));
 }
 return map;
}

Answer 6

In the second for-loop, you need to access the Map you get as a value from the outer loop. You also need to change the type of the Entry in the second loop.

Try this code:

for (Entry<Character, Map<Integer, Double>> outer : MapInsideOfAMap.entrySet()) {
 System.out.println("Key: " + outer.getKey() + "\n");
 for (Entry<Integer, Double> inner : outer.getValue().entrySet()) {
 System.out.println("Key = " + inner.getKey() + ", Value = " + inner.getValue());
 }
}

Answer 7

But the complexity of the structure is probably redundant.

public static void print(char keyData, Map<Character, Map<Integer, Double>> fromData) {
 System.out.println("print: " + get(keyData, fromData));
}
public static Map<Integer, Double> get(char keyData, Map<Character, Map<Integer, Double>> fromData) {
 for (Map.Entry<Character, Map<Integer, Double>> entry : fromData.entrySet()) {
 Character key = entry.getKey();
 if(key.equals(keyData))
 return entry.getValue();
 }
 return Collections.emptyMap();
}