adoptopenjdk / lambda-tutorial

Exercises to learn lambda syntax + the Streams API from the upcoming JDK 8 release

Lambda Tutorial

A set of exercises to teach use of Java 8 lambda syntax, and the Streams API.

To follow the exercises:

• fork and clone the repository
• ensure you have a correctly configured, JDK8+ build
  • Maven can help generate configuration for your favourite IDE
  • ensure your cloned project, particularly the class ConfigureYourLambdaBuildOfJdk compiles and runs correctly
• navigate to the first exercise, Exercise_1_Test (tests are in src/test/java, in the package org.adoptopenjdk.lambda.tutorial)
• read background information in the JavaDoc, and follow instructions, making the test pass
• to find solutions check out different branches of the project. Two flavours of solutions are available: what it might have looked like before JDK 8, and what it might look like after JDK 8. Those are in branches solutions-prejava8 and solutions-postjava8 respectively.

Exercises

1. Internal vs External Iteration (the forEach method)
2. Filtering and Collecting
3. Mapping
4. Method References
5. Default methods on interfaces

lambda-tutorial's Issues

Enhance Maven POM so it contains the usual sections to create a Maven site

Exercise 1, Test 3 should present syntax for having multiple statements in a lambda expression

The solution for Exercise 1, Test 3 requires that multiple statements are executed in a single lambda. However, the syntax for doing has not been introduced.

The fix would be to put an example of that syntax somewhere in the JavaDocs.

Add GPLv2 License headers to files and the LICENSE file iteself

This can be done 'automatically' via the maven license plugin that will shortly be supplied to this project.

Exercise 1, Test 3 should be more similar to Test 2

Exercise_1_Test has one test case which requires Shape#toString method, and the following test case expects the use of Shape#getColor to build the result string. The latter test case should just use Shape#toString, for consistency.

Excercise 2 - Person, Ballot and RegisteredVoter classes should have encapsulated Getters

Following OO principles of not having public access to private members

Javadoc comments for Tutorial should be formatted using latest Java7/8 javadoc stds

Whilst there's not too many classes to overhaul, this is a good opportunity to get this right early. + package-info files as well.

Exercise_5_Test.java fails to compile

The source files for the following classes seem to be missing: StarRating, UserRatedMusicLibrary, CloudScrobblingMusicLibrary, UserRatedLocalFilesystemMusicLibrary.

The following imports do not resolve:

import org.adoptopenjdk.lambda.tutorial.exercise5.musicplayer.StarRating;
import org.adoptopenjdk.lambda.tutorial.exercise5.musicplayer.UserRatedMusicLibrary;
import org.adoptopenjdk.lambda.tutorial.exercise5.thirdpartyplugin.CloudScrobblingMusicLibrary;
import org.adoptopenjdk.lambda.tutorial.exercise5.thirdpartyplugin.UserRatedLocalFilesystemMusicLibrary;

Update to more recent JDK state

This is a great learning project.

However I’ve noticed a lot of the content is focused on either EA or earlier versions of IDEs (in a Wiki) or compatible JDK.

Given latest versions of JDK (as if request 14-15) and with new release schedule, suggest

(1) updating JDK references in readme and source where applicable
(2) for IDE setup wiki pages changes since JDK 8 is readily supported if not mandatory now with recent IDE versions.