Java 8 Lambdas Hands-on Lab Materials

(version for late 2016 conferences)

Open LambdaLab in your favorite IDE. (Currently NetBeans is supported.) Then open the files in

Test Packages > exercises

The exercises are in the form of JUnit tests. Each exercise is a single test method. Each test method is initially marked with @Ignore so that it will be not be run by JUnit. Each test method has some setup code and some assertions at the bottom.

To work on an exercise, uncomment @Ignore and then look for a "TODO" comment somewhere in the body of the test method. Add code here that makes the assertions pass. You shouldn't have to modify any of the setup code at the top of the test method or the assertions at the bottom of the test method.

There is sometimes a hint or two after a test method. If you're having trouble with an exercise, look for hints. The hint text is inside a editor fold that is closed by default, so click on the plus-sign to read it.

The intent of the exercises is to solve them using the new Java 8 lambda feature, the new Java 8 Streams API, and other APIs added in Java 8. Of course, it is possible to use conventional Java code, e.g., for-loops, but all of the exercises are amenable to being solved using new Java 8 features in just a handful of lines. Most exercises will take less than half a dozen lines. Some of the more difficult exercises may take up to eight lines, depending upon how aggressive you are about breaking lines. None of the exercises involve writing large amounts of code. Most of the streams-based exercises involve writing a single stream pipeline.

Each exercise has one or two hints hidden in a code fold below the exercise. Open these up if you're stuck.

Several of the exercises read data from a text file. The field named "reader" is a BufferedReader which will be opened for you on the text file. In any exercise that refers to reading from the text file, you can simply use the "reader" variable without worry about opening or closing it. This is set up by JUnit using the @Before and @After methods at the bottom of the file. The text file is "SonnetI.txt" (Shakespeare's first sonnet) which is located at the root of this NetBeans project.

If you're really stuck, the solutions to the exercises are in the file Test Packages / solutions / Exercises.java. Many exercises can be solved in several different ways. In some cases, the solutions file will have several alternatives. Even if you've solved an exercise, it can be useful to look at the solutions to compare your solutions with those of the lab authors.