What Java 17’s Stream SIZED Feature Means for skip() and limit()

Introduction

Java 17, released on September 14, is a long‑term support (LTS) version that brings several changes, including a new SIZED characteristic for the Stream API.

Java 17 Stream SIZED Feature

Starting with Java 17, a stream marked as SIZED retains its size information, so operations such as skip() and limit() remain effective during processing. This can change the observable behavior of a stream.

long count = Stream.of(1, 2, 3, 4)
    .skip(1)
    .limit(2)
    .peek(System.out::println)
    .count();
System.out.println("count:\t" + count);

In Java 8‑16 the peek call would print the values 2 and 3, but in Java 17 it prints nothing because the stream size is known in advance and the elements need not be traversed.