IntStream reduce(int identity, IntBinaryOperator op) in Java with Examples

IntStream reduce(int identity, IntBinaryOperator op) performs a reduction on the elements of this stream, using the provided identity value and an associative accumulation function, and returns the reduced value.

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 :

int reduce(int identity,  IntBinaryOperator op)

Parameters :



  • identity : The identity value for the accumulating function.
  • 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 : The result of the reduction.

Example 1 :

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// Java code for IntStream reduce
// (int identity, IntBinaryOperator op)
import java.util.*;
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 IntStream reduce
        // (int identity, IntBinaryOperator op)
        int answer = stream.reduce(0, (num1, num2)
                                          -> (num1 + num2) * 2);
  
        // Displaying the result
        System.out.println(answer);
    }
}

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Output :

176

Example 2 :

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// Java code for IntStream reduce
// (int identity, IntBinaryOperator op)
import java.util.*;
import java.util.stream.IntStream;
  
class GFG {
  
    // Driver code
    public static void main(String[] args)
    {
        // Creating an IntStream
        IntStream stream = IntStream.range(4, 10);
  
        // Using IntStream reduce
        // (int identity, IntBinaryOperator op)
        int answer = stream.reduce(0, (num1, num2)
                                          -> (num1 + num2) - 2 * (num1 - num2));
  
        // Displaying the result
        System.out.println(answer);
    }
}

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Output :

9


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