Understanding the Differences Between Stream and IntStream in Java

Java 8 introduced the Stream API, a powerful new abstraction for working with sequences of data in a functional programming style. Among the various features of the Stream API, two that often cause confusion are Stream<Integer> and IntStream. In this blog post, we’ll explore the differences between these two types of streams.

What is Stream<Integer>?

Stream<Integer> is a stream of Integer objects. Integer is a wrapper class for the primitive int type in Java. This means that a Stream<Integer> can contain null values, and additional memory is used for object metadata (like the class pointer and the object header).

Here’s an example of a Stream<Integer>:

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

What is IntStream?

IntStream is a stream of primitive int values. It’s part of the Java 8 Stream API’s support for streams of primitive values, along with LongStream and DoubleStream. IntStream can’t contain null values, and it uses less memory than Stream<Integer> because it doesn’t need to store object metadata.

Here’s an example of an IntStream:

int[] array = {1, 2, 3, 4, 5};
IntStream stream = Arrays.stream(array);

Key Differences

The main differences between Stream<Integer> and IntStream are:

1. Memory Usage: Stream<Integer> uses more memory than IntStream because it needs to store object metadata for each element.
2. Null Values: Stream<Integer> can contain null values, but IntStream can’t.
3. Available Operations: IntStream has additional operations for numerical computation, such as sum, average, min, max, etc. These operations are not available in Stream<Integer>.
4. Conversion: You can convert a Stream<Integer> to an IntStream using the mapToInt operation, like this:

Stream<Integer> integerStream = Arrays.asList(1, 2, 3, 4, 5).stream();
IntStream intStream = integerStream.mapToInt(Integer::intValue);

Conclusion

While Stream<Integer> and IntStream might seem similar at first glance, they have important differences. Understanding these differences is key to using the Java 8 Stream API effectively and efficiently.

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