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Create String from an array in Java

String.join(",", collection);

The above statement uses join function within the String class to join the elements of the collection into the String. The elements are joint using the specified delimiter which is a “,” in this case.

final List<String> collection = new ArrayList<>();
collection.add("Hello");
collection.add("World");

final String joinedString = String.join(",", collection);

System.out.println(joinedString);

The above examples joins an array list collection of Strings to create a single comma delimited string.

Output

Hello,World

Integer Collection to String

The String.join function only works on String collections. However if you do happen to have a collection of Integers and need to join these integers into a single string delimited by comma, the below example shows how.

final  List<Integer> intList = new ArrayList<>();
intList.add(10);
intList.add(20);
intList.add(30);

final String joinedIntString = String.join(",", intList.stream().map(x -> "" + x).collect(Collectors.toList()));

System.out.println(joinedIntString);

Output

10,20,30

The .map function maps each Integer element into a String element simply by appending the Integer to an empty string.

 

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