DoubleStream reduce(DoubleBinaryOperator op) in Java
DoubleStream reduce(DoubleBinaryOperator op) performs a reduction on the elements of this stream, using an associative accumulation function, and returns an OptionalDouble 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 :
OptionalDouble reduce(DoubleBinaryOperator op)
Parameters :
- OptionalDouble : A container object which may or may not contain a long value. If a value is present, isPresent() will return true and getAsDouble() will return the value.
- DoubleBinaryOperator : An operation upon two double-valued operands and producing a double-valued result.
- op : An associative, stateless function for combining two values.
Return Value : An OptionalDouble describing the reduced value, if any.
Example 1 :
import java.util.OptionalDouble;
import java.util.stream.DoubleStream;
class GFG {
public static void main(String[] args)
{
DoubleStream stream = DoubleStream.of( 1.2 , 2.3 , 3.4 , 4.5 );
OptionalDouble answer = stream.reduce(Double::sum);
if (answer.isPresent()) {
System.out.println(answer.getAsDouble());
}
else {
System.out.println( "Stream is empty" );
}
}
}
|
Output :
11.4
Example 2 :
import java.util.OptionalDouble;
import java.util.stream.DoubleStream;
class GFG {
public static void main(String[] args)
{
DoubleStream stream = DoubleStream.of( 1.2 , 2.3 , 3.4 , 4.5 );
OptionalDouble answer = stream.reduce((a, b)
-> (a * b) * (a * b));
if (answer.isPresent()) {
System.out.println(answer.getAsDouble());
}
else {
System.out.println( "Stream is empty" );
}
}
}
|
Output :
9111992.471343633
Last Updated :
06 Dec, 2018
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