Reduce in stream in java

// Identity – an element that is the initial value of the reduction operation and the default result if the stream is empty
// Accumulator – a function that takes two parameters: a partial result of the reduction operation and the next element of the stream
// Combiner – a function used to combine the partial result of the reduction operation when the reduction is parallelized or when there's a mismatch between the types of the accumulator arguments and the types of the accumulator implementation

import java.util.*; 
import java.util.stream.*;

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
int result = numbers
  .stream()
  .reduce(0, (subtotal, element) -> subtotal + element); // Didn't use a combiner here

// A combiner should be used when objects are used in accumulator parameters
// Only then, it works

List<User> users = Arrays.asList(new User("John", 30), new User("Julie", 35));
int result = users.stream()
  .reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
// Integer::sum is a combiner which is a function for the desired operation.

Source: baeldung.com

Similar codes

3 votes157 views4 answers
Round corner imageview android
Java
4 votes139 views2 answers
Get number of lines in a file java
Java
2 votes122 views1 answer
Remove event listener
Java
1 vote162 views1 answer
Java program to get the circle radius
Java
11 votes158 views4 answers
How to read a text file in java
Java
0 vote156 views1 answer
Java integer division to float
Java
0 vote212 views1 answer
UserRedirectRequiredException: A redirect is required to get the users approval spring boot 5 security
Java Spring
22 votes152 views3 answers
Java int array
Java
14 votes155 views3 answers
Arraylist add method
Java
0 vote167 views2 answers
Hackerearth test
Java