Introduction to Programming

concat(Stream a, Stream b)

The Stream<T> concatenate (Stream<> a, Stream<T> b) static method of the Stream interface creates a stream of values based on two Stream objects, a and b, passed in as the parameters. The newly created stream consists of all the elements of the first parameter, a, followed by all of the elements of the second parameter, b. The following code demonstrates this method of Stream object creation:

Stream<Integer> stream1 = List.of(1, 2).stream();Stream<Integer> stream2 = List.of(2, 3).stream();Stream.concat(stream1, stream2)        .forEach(System.out::print);        //prints: 1223

Notice that the 2 element is present in both original streams, and consequently, it is present twice in the resulting stream.