Stream sorted() in Java

Stream.sorted() is an intermediate, stateful operation that returns a stream with elements sorted in natural order or by a given Comparator. It is stable for ordered streams, requires elements to be Comparable (or a comparator), and may throw ClassCastException if elements are not comparable.

Example:

import java.util.*;
class GFG {
    public static void main(String[] args) {
        List<Integer> list = Arrays.asList(-9, -18, 0, 25, 4);

        list.stream().sorted().forEach(System.out::println);
    }
}

-18
-9
0
4
25

Explanation:

• list.stream() converts the list into a stream.
• sorted() arranges elements in their natural (ascending) order.
• forEach() prints each sorted element.

Syntax

Stream<T> sorted()

• Paramerter: "T" type of stream elements.

Example 1: This code demonstrates how Stream.sorted() sorts elements of a stream in natural order without modifying the original collection.

import java.util.*;
class GFG {
    public static void main(String[] args) {
        List<String> list = Arrays.asList("Geeks", "for", "Geeks", "Welcome", "You");
        list.stream().sorted().forEach(System.out::println);
    }
}

Geeks
Geeks
Welcome
You
for

Explanation:

• .sorted() sorts the stream elements in their natural order (alphabetically for strings).
• The original list remains unchanged; only the stream is sorted.

Example 2: This code demonstrates sorting a stream of Point objects by their x coordinate using Stream.sorted() with a custom comparator.

import java.util.*;
class Point {
    Integer x, y;
    Point(Integer x, Integer y) {
        this.x = x;
        this.y = y;
    }
    public String toString() {
        return x + ", " + y;
    }
}
class GFG {
    public static void main(String[] args) {
        List<Point> list = Arrays.asList(
            new Point(10, 20),
            new Point(5, 10),
            new Point(1, 100),
            new Point(50, 2000)
        );
        list.stream()
            .sorted((p1, p2) -> p1.x.compareTo(p2.x))
            .forEach(System.out::println);
    }
}

1, 100
5, 10
10, 20
50, 2000

Explanation:

• .sorted((p1, p2) -> p1.x.compareTo(p2.x)) sorts the points based on their x coordinate.
• Sorting is stable; the original list is not modified.