CODEWITHSUNDEEP
java
Hami
Hami

Reputation: 111

How can I use additional checks in the for loop considering Hashmap?

I have created two hashmaps and I want to iterate both of them inside the same for loop. 

HashMap<String,Double> hashmapA = new HashMap<>();
HashMap<String,Double> hashmapB = new HashMap<>();

So, if I iterate the elements in hashmapA as follows:

for(String map1:hashmapA.keyset()){
...
}

How can I iterate the values of hashmapB inside the same loop? Actually, I don't want to use the inner loop.

Upvotes: 0

Views: 56

Answers (2)

dan1st
dan1st

Reputation: 16457

If you just want to iterate over all keys:

Just create a new HashSet out of the keys of the first Map and add the keys of the second Map:

Collection<Map.Entry<String,Double>> entries=new HashSet<>(hashmapA.entrySet());
keys.addAll(hashmapB.entrySet());
for(Map.Entry<String,Double> entry:entries){
    String key=entry.getKey();
    Double value=entry.getValue();
    ...
}

This can also be done using Java 8 Streams:

for(Map.Entry<String,Double> entry: Stream.concat(hashmapA.entrySet().stream(),hashmapB.entrySet().stream()){
     String key=entry.getKey();
    Double value=entry.getValue();
    ...
}

If you just want the intersection of the maps, you can use:

Collection<String> keys=new HashSet<>(hashmapA.keySet());
keys.retainAll(hashmapB.keySet());
for(String key:keys){
    Double aValue=hashmapA.get(key);
    Double bValue=hashmapB.get(key);
    ...
}

Or (with Streams):

for(String key: hashmapA.entrySet().stream().filter(k->hashmapB.containsKey(k))){
    Double aValue=hashmapA.get(key);
    Double bValue=hashmapB.get(key);
    ...
}

As @bsaverino stated in the comments:

Regarding your latest remark @Hami then just iterating over the keys of hashmapA and using hashmapB.containsKey(...) could have been enough.

The following will also work in your case:

for(String key:hashmapA.keySet()){
    if(hashmapB.containsKey(key){
        Double aVal=hashmapA.get(key);
        Double bVal=hashmapB.get(key);
    }
}

Upvotes: 1

Ryuzaki L
Ryuzaki L

Reputation: 40078

Iterator is one of the best choice either with keyset or entrySet

Iterator hmIterator1 = hashmapA.entrySet().iterator(); 
Iterator hmIterator2 = hashmapB.entrySet().iterator(); 

 while (hmIterator1.hasNext() && hmIterator2.hasNext()) { 

       hmIterator1.next();
       hmIterator2.next();

    }

Upvotes: 1

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