LongStream reduce(LongBinaryOperator op) in Java
Last Updated :
06 Dec, 2018
LongStream reduce(LongBinaryOperator op) performs a reduction on the elements of this stream, using an associative accumulation function, and returns an OptionalLong describing the reduced value, if any.
A reduction operation or fold takes a sequence of input elements and combines them into a single summary result, such as finding the sum or maximum of a set of numbers. An operator or function op is associative if the following holds :
(a op b) op c == a op (b op c)
This is a terminal operation i.e, it may traverse the stream to produce a result or a side-effect. After the terminal operation is performed, the stream pipeline is considered consumed, and can no longer be used.
Syntax :
OptionalLong reduce(LongBinaryOperator op)
Parameters :
- OptionalLong : A container object which may or may not contain a long value. If a value is present, isPresent() will return true and getAsLong() will return the value.
- LongBinaryOperator : An operation upon two long-valued operands and producing a long-valued result.
- op : An associative, stateless function for combining two values.
Return Value : An OptionalLong describing the reduced value, if any.
Example 1 :
import java.util.OptionalLong;
import java.util.stream.LongStream;
class GFG {
public static void main(String[] args)
{
LongStream stream = LongStream.of(9L, 10L, 11L, 12L);
OptionalLong answer = stream.reduce(Long::sum);
if (answer.isPresent()) {
System.out.println(answer.getAsLong());
}
else {
System.out.println( "no value" );
}
}
}
|
Output :
42
Example 2 :
import java.util.OptionalLong;
import java.util.stream.LongStream;
class GFG {
public static void main(String[] args)
{
LongStream stream = LongStream.of(9L, 10L, 11L, 12L);
OptionalLong answer = stream.reduce((a, b) -> 2 * (a * b));
if (answer.isPresent()) {
System.out.println(answer.getAsLong());
}
else {
System.out.println( "no value" );
}
}
}
|
Output :
95040
Like Article
Suggest improvement
Share your thoughts in the comments
Please Login to comment...