CODEWITHSUNDEEP
javacollectionsdictionaryhashmap
agyarenk
agyarenk

Reputation: 1

Contains if and only if in the Collection class- Java

Map<String, Integer> successors = new HashMap <String, Integer> ();
// I have added some elements into the successors.
 Collection<Integer> uniqueValues = successors.values();

Is there a way for me to find out in java if uniqueValues can show me that all the values in it are the same?

I planned on using the if(uniqueValues.contains(1))statement. But I just could not figure it out. Since this statement will say true if 1 is present and other values different from 1 are also present. I just want it to return true if 1 is the only value in the collections.

eg; {1,1,1,1,1,1,1,1,1,1,1,1,1} should return true. But {1,2,1,3,1,4,2,4,22,1,1,1,4} should return false.

Some code along the lines of "Contains if and only if."
This will be of great help. Thanks in advance.

Upvotes: 0

Views: 4718

Answers (3)

Petr Mensik
Petr Mensik

Reputation: 27526

Some sort of Set sounds like easiest solution 

if(new HashSet<Integer>(successors.values)).size() == 1)

Because Set can contain only unique values, logical consequence of having input collection with same values is the Set of size one. Or you can of course introduce you own util method which will check this condition.

Upvotes: 1

Elliott Frisch
Elliott Frisch

Reputation: 201497

Well, you could do something like this (inefficiently),

boolean uniqueValues = new HashSet<Integer>(successors.values()).size() == 1;

Since that will check every value every time, a more efficient approach might be,

boolean uniqueValues = true;
Collection<Integer> values = successors.values();
Iterator<Integer> iter = values.iterator();
if (iter.hasNext()) {
  int t = iter.next();
  while (iter.hasNext()) {
    int i = iter.next();
    if (t != i) {
      // stop if we find a different value
      uniqueValues = false;
      break;
    }
  }   
}

Upvotes: 1

Tassos Bassoukos
Tassos Bassoukos

Reputation: 16152

Do it the CPU-clock-wasting way:

 if(new HashSet(successors.values()).size()>1) {...}

Upvotes: 2

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