CODEWITHSUNDEEP
javastringlistfor-loopdictionary
R Jackson
R Jackson

Reputation: 105

Create a Java for loop to concatenate 2 sets of strings

I have Map<String, String> prefixes

and List<String> annotationProperties

And I am trying to get the string output of prefix: annotationProperty for each entry (they were entered in order).

Is there a for loop I could use to concatenate these? I need to return the entries as a List<String> to use in an XML output.

Thank you!

Upvotes: 0

Views: 87

Answers (1)

flakes
flakes

Reputation: 23634

I assume annotationProperties is a key for prefix map. If that is the case then in Java 8 you can do this:

List<String> output = annotationProperties.stream()
        .map(prop -> String.format("%s: %s",  prefix.get(prop), prop))
        .collect(Collectors.toList());

stream is called so you can use stream functions such as map and collect

map is called to transform the strings in annotationProperties into your desired output

and collect is called to convert the stream back into a list

If you want to use a for loop then you could also do it like this:

// The end size is known, so initialize the capacity.
List<String> output = new ArrayList<>(annotationProperties.size());
for (String prop : annotationProperties){
    output.add(String.format("%s: %s",  prefix.get(prop), prop));
}

Can a set a variable equal to .collect(Collectors.toList()); ?

We already have one! In both cases we made a variable output which is a list of Strings formatted as prefix: property. If you want to use this list then you can loop over it like this:

for (String mystring : output) {
    // do xml creation with mystring
}

or like this:

for (int i = 0; i < output.size(); i++){
    String mystring = output.get(i);
    // do xml creation with mystring
}

or like this:

output.stream().forEach(mystring -> {
    // do xml creation with mystring
});

Upvotes: 1

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