IntStream reduce(IntBinaryOperator op) performs a reduction on the elements of this stream, using an associative accumulation function, and returns an OptionalInt 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 :
OptionalInt reduce(IntBinaryOperator op)
Parameters :
- OptionalInt : A container object which may or may not contain a int value. If a value is present, isPresent() will return true and getAsInt() will return the value.
- IntBinaryOperator : An operation upon two int-valued operands and producing an int-valued result.
- op : An associative, stateless function for combining two values.
Return Value : An OptionalInt describing the reduced value, if any.
Example 1 :
// Java code for IntStream reduce // (IntBinaryOperator op) import java.util.OptionalInt;
import java.util.stream.IntStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating an IntStream
IntStream stream = IntStream.of( 2 , 3 , 4 , 5 , 6 );
// Using OptionalInt (a container object which
// may or may not contain a non-null value)
// Using IntStream reduce(IntBinaryOperator op)
OptionalInt answer = stream.reduce(Integer::sum);
// if the stream is empty, an empty
// OptionalInt is returned.
if (answer.isPresent()) {
System.out.println(answer.getAsInt());
}
else {
System.out.println( "no value" );
}
}
} |
Output :
20
Example 2 :
// Java code for IntStream reduce // (IntBinaryOperator op) import java.util.OptionalInt;
import java.util.stream.IntStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating an IntStream
IntStream stream = IntStream.of( 2 , 3 , 4 , 5 , 6 );
// Using OptionalInt (a container object which
// may or may not contain a non-null value)
// Using IntStream reduce(IntBinaryOperator op)
OptionalInt answer = stream.reduce((a, b) -> (a * b));
// if the stream is empty, an empty
// OptionalInt is returned.
if (answer.isPresent()) {
System.out.println(answer.getAsInt());
}
else {
System.out.println( "no value" );
}
}
} |
Output :
720