jOOλ

jOOλ is part of the jOOQ series (along with jOOQ, jOOX, jOOR, jOOU) providing some useful extensions to Java 8 lambdas. It contains these classes:

org.jooq.lambda.function

Why only Function and BiFunction? We have also included support for Function1 through Function8.

org.jooq.lambda.tuple

Tuple support is essential in functional programming. A variety of things can be modelled as tuples, e.g. function argument lists. This is why we support type safe Tuple1 through Tuple8 types.

org.jooq.lambda.Seq

The new Streams API was implemented with a strong focus on parallelisation. Many of the useful methods that we know from other functional languages (e.g Scala) are missing. This is why jOOλ knows a Seq interface that extends Stream and adds a variety of additional methods to, such as:

// (1, 2, 3, 4, 5, 6)
Seq.of(1, 2, 3).concat(Seq.of(4, 5, 6));

// (tuple(1, "a"), tuple(2, "b"), tuple(3, "c"))
Seq.of(1, 2, 3).zip(Seq.of("a", "b", "c"));

// ("1:a", "2:b", "3:c")
Seq.of(1, 2, 3).zip(Seq.of("a", "b", "c"), (x, y) -> x + ":" + y);

// tuple((1, 2, 3), (a, b, c))
Seq.unzip(Seq.of(tuple(1, "a"), tuple(2, "b"), tuple(3, "c")));

// (tuple("a", 0), tuple("b", 1), tuple("c", 2))
Seq.of("a", "b", "c").zipWithIndex();

// (3, 4, 5)
Seq.of(1, 2, 3, 4, 5).skipWhile(i -> i < 3);

// (3, 4, 5)
Seq.of(1, 2, 3, 4, 5).skipUntil(i -> i == 3);

// (1, 2)
Seq.of(1, 2, 3, 4, 5).limitWhile(i -> i < 3);

// (1, 2)
Seq.of(1, 2, 3, 4, 5).limitUntil(i -> i == 3);

// (1, 0, 2, 0, 3, 0, 4)
Seq.of(1, 2, 3, 4).intersperse(0);

// "abc"
Seq.of("a", "b", "c").foldLeft("", (u, t) -> t + u);

// "cba"
Seq.of("a", "b", "c").foldRight("", (t, u) -> t + u);

// tuple((1, 2, 3), (1, 2, 3))
Seq.of(1, 2, 3).duplicate();

// tuple((1, 3, 5), (2, 4, 6))
Seq.of(1, 2, 3, 4, 5, 6).partition(i -> i % 2 != 0)

// tuple((1, 2), (3, 4, 5))
Seq.of(1, 2, 3, 4, 5).splitAt(2);

// tuple(1, (2, 3, 4, 5))
Seq.of(1, 2, 3, 4, 5).splitAtHead();

// (2, 3)
Seq.of(1, 2, 3, 4, 5).slice(1, 3)

org.jooq.lambda.Unchecked

Lambda expressions and checked exceptions are a major pain. Even before going live with Java 8, there are a lot of Stack Overflow questions related to the subject:

• http://stackoverflow.com/q/18198176/521799
• http://stackoverflow.com/q/19757300/521799
• http://stackoverflow.com/q/14039995/521799

The Unchecked class can be used to wrap common @FunctionalInterfaces in equivalent ones that are allowed to throw checked exceptions. E.g. this painful beast:

Arrays.stream(dir.listFiles()).forEach(file -> {
    try {
        System.out.println(file.getCanonicalPath());
    }
    catch (IOException e) {
        throw new RuntimeException(e);
    }

    // Ouch, my fingers hurt! All this typing!
});

... will become this beauty:

Arrays.stream(dir.listFiles()).forEach(
    Unchecked.consumer(file -> { System.out.println(file.getCanonicalPath()); })
);

org.jooq.lambda.SQL

JDBC should be as simple as this in Java 8:

SQL.stream(stmt, Unchecked.function(r ->
    new SQLGoodies.Schema(
        r.getString("FIELD_1"),
        r.getBoolean("FIELD_2")
    )
))
.forEach(System.out::println);

(where SQLGoodies.Schema is just an ordinary POJO).

For more details and other options to write SQL in Java 8, visit this website here:

http://www.jooq.org/java-8-and-sql