Java Stream reduce

int result = numbers.stream().reduce(0, Integer::sum);
assertThat(result).isEqualTo(21);
 
// alternative function call with binary functions
BiFunction<Boolean, BooleanExpression, Boolean> acc = (x, y) -> x && y.evaluate(context);
expressions.stream().reduce(true, acc, (x,y) -> x && y); // returns a boolean

• Calls a Reducer Function that is a binary function
• First argument is the identity for the reducer
• Second argument is the accumulator: a Java BinaryOperator
• Third argument is the combiner: a Java BinaryOperator used to combine result of reduction if the function is Parallelized (Java Parallel Stream)