How is the reduce function used in Java?

In Java, the reduce function is used to combine elements in a collection. It takes a binary operator and applies it to the elements in the collection, returning a combined result.

Here is how the reduce function is used:

T reduce(T identity, BinaryOperator<T> accumulator)

Identity is used as a return value when the set is empty, and the accumulator is a binary operator that defines how two elements are combined into one result.

Example of using the reduce function:

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);

int sum = numbers.stream()
                .reduce(0, (a, b) -> a + b);
System.out.println("Sum: " + sum); // 输出：Sum: 15

In the example above, we used the reduce function to add up the elements in the collection, starting with an initial value of 0. The final result is 15.

In addition to the above-mentioned uses, the reduce function can also be used for more complex operations, such as calculating maximum and minimum values, string concatenation, and more. The specific usage can be flexibly applied according to specific needs.