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Java 8 - Streams - Collectors - Joining


  • joining operation on Collectors provides a way to aggregate the result of a stream operation into a concatenated string.
  • There are two implementations. The first simply concatenates the stream items, while the second concatenates the items with a delimiter.

stream of employees
Stream employees = Stream.of( new Employee("Joe", "Blogs", "Sales", 100.0), new Employee("Richardo", "Banks", "Engineering", 50.0), new Employee("Hewlet", "Packer", "Marketing",40.0) );

another stream of employees
Stream employees_2 = Stream.of( new Employee("Ruben", "Paul", "Sales", 100.0), new Employee("Shelly", "Smith", "Engineering", 50.0) ); 

USAGE

 collecting stream of transformation result in a concatenated string
 String LastNames = employees .map(employee -> employee.getLastName()) .collect(Collectors.joining());

collecting stream of transformation result in a comma-separated string
String LastNamesCommaSeparated = employees_2 .map(employee -> employee.getLastName()) .collect(Collectors.joining(", "));

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