How to use intermediate stream operations in JShell in Java 9?

JShell is a tool introduced in Java 9, and it accepts simple statements like expressions, variables, methods, classes, etc.. as input and produces immediate results.

A Stream is a sequence of values. An intermediate stream operation is an operation that takes a stream. For instance, it can be applied to a lambda expression and produces another stream of elements as its result.

The most popular intermediate stream operations are mentioned below:

• 1) sorted(): This method preserves the elements of the consumed stream as a result but also puts them in natural sorted order.
• 2) distinct(): This method returns a stream retaining only unique elements of the input stream, and it can maintain the relative order of retained elements.
• 3) filter(): This method can be used to filter stream elements based on some logic.
• 4) map(): This method applies lambda expression to compute new results from input stream elements. Then, it returns a stream of these results as output.

In the below code snippet, we can implement different intermediate stream operations in the JShell tool.

Snippet

jshell> List<Integer> numbers = List.of(3, 10, 23, 200, 77, 9, 32);
numbers ==> [3, 10, 23, 200, 77, 9, 32]

jshell> numbers.stream().sorted().forEach(elem -> System.out.println(elem));
3
9
10
23
32
77
200

jshell> List<Integer> numbers = List.of(3, 5, 54, 280, 5, 9, 40);
numbers ==> [3, 5, 54, 280, 5, 9, 40]

jshell> numbers.stream().distinct().forEach(elem -> System.out.println(elem));
3
5
54
280
9
40

jshell> numbers.stream().distinct().sorted().forEach(elem -> System.out.println(elem));
3
5
9
40
54
280

jshell> numbers.stream().distinct().map(num -> num * num).forEach(elem -> System.out.println(elem));
9
25
2916
78400
81
1600

raja

Updated on: 23-Apr-2020

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