replace duplicate values string in hashmap java

Question

I have a hashmap which contains student id as key and some string as value. It contains data like

a abc.txt
b cde.txt
d abc.txt

I want to find the duplicate values in map and replace them with genreic values. I want a map like

a abc.txt
b cde.txt
d abc_replacevalue.txt

I have tried with the code but its not working

Map<String,String> filemap = new HashMap<String,String>();
// filemap is the original hash map..

Set<String> seenValues = new HashSet<String>();
Map<String, String> result = new HashMap<String, String>();

for (Map.Entry<String, String> entry : filemap.entrySet()) {
    String value = entry.getValue();

    if (seenValues.contains(value)) {
        value = "updated"; // update value here
    }
    result.put(entry.getKey(), value);
    seenValues.add(value);
}

for (String key : result.keySet() ) {
    String value = result.get( key );
    System.out.println(key + " = " + value);
}

The output is still the same

a abc.txt
b cde.txt
d abc.txt

Matthew Franglen · Accepted Answer · 2015-02-04 12:07:13Z

2

You can generate a new map from an existing one, checking every new value that you come across to see if it has already been seen:

Set<String> seenValues = new HashSet<String>();
Map<String, String> result = new HashMap<String, String>();

for (Map.Entry<String, String> entry : original.entrySet()) {
    String value = entry.getValue();

    if (seenValues.contains(value)) {
        value = ...; // update value here
    }
    result.put(entry.getKey(), value);
    seenValues.add(value);
}

answered Feb 4, 2015 at 12:07

Matthew Franglen

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3 Comments

Matthew Franglen Over a year ago

You need to add the updated value anyway so that doesn't actually save anything.

Matthew Franglen Over a year ago

The add that I call can add the updated value, while your one only adds the original value. If you need to update the value within the if block and then add it then you have two calls to add, one of which is also a membership test. Instead I have one membership test and one add.

Tom Over a year ago

-.- .... you're absolutely right. I missed, that this call adds the updated value. Nevermind, everything is alright :D.

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