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

0 vote194 views1 answer
Android send fragment context
Java
0 vote174 views1 answer
Arraylist how to add at 0 java
Java
0 vote178 views1 answer
Case sensitive in java
Java
0 vote167 views1 answer
Height constraint layout guideline
Java
0 vote197 views1 answer
Java windowbuilder multiple monitors windowed mode
Java
0 vote220 views1 answer
Validation failed for query for method public abstract java.util.List
Java
4 votes173 views3 answers
Volley android
Java
1 vote168 views1 answer
Fast Lookup of Java
Java
4 votes172 views1 answer
Java remove from arraylist while iterating
Java
4 votes180 views2 answers
Remove action bar android studio
Java