Intuitive generics based functional interfaces with support for void, returns, multiple params and exceptions.

Dependencies

• Zero. JDK8 compatible. Tested on JDK15.

Maven dependencies available on maven central search.maven.org

Dependency

<dependency>
    <groupId>com.momomo</groupId>
    <artifactId>momomo.com.platform.Lambda</artifactId>
    <version>5.0.2</version>
</dependency>                                                      

Repository

<repository>
    <id>maven-central</id>
    <url>http://repo1.maven.org/maven2</url>
</repository>

Our other, highlighted repositories

• momomo.com.platform.Core Is essentially what makes the our the core of several of momomo.com's public releases and contains a bunch of Java utility.

• momomo.com.platform.Obj Intuitive library that makes it easier for you to return multiple, fully defined objects on the fly from any method, any time rather than being limited to the default maximum of one.

• momomo.com.platform.Nanotime Allows for nanosecond time resolution when asking for time from Java Runtime in contrast with System.currentTimeMillis().

• momomo.com.platform.DB.transactional.Hibernate A library to execute database commands in transactions without having to use annotations based on Hibernate libraries. No Spring!

• momomo.com.platform.DB.transactional.Spring A library to execute database commands in transactions without having to use annotations based on Spring libraries.

Background

Ever confused by names like Supplier, Function, BiFunction, Consumer, ... and so forth? Do you find them limiting?

Are you easily able to keep track of them? Can your brain parse them quickly enough when scanning method signatures?

Can you easily convert and/or go from one method to another?

With this intuitive interface based naming strategy you can use:

• Lambda.R    for a return lambda with defined return type that takes 0 defined parameters. Implements Supplier<Return>.
• Lambda.R1   for a return lambda with defined return type that takes 1 defined parameter. Implements Function<Param1, Return>.
• Lambda.R2   for a return lambda with defined return type that takes 2 defined parameter. Implements BiFunction<Param1, Param2, Return>.
• Lambda.R2E  for a return lambda with defined return type that takes 2 defined parameters, and allows you to define the thrown exception type as well.
• ...
• Lambda.V    for a void lambda that takes 0 defined parameters. Implements Runnable.
• Lambda.V1   for a void lambda that takes 1 defined parameter. Implements Consumer<Param1>.
• Lambda.V2   for a void lambda that takes 2 defined parameters. Implements BiConsumer<Param1>.
• Lambda.V2E for a void lambda that takes 2 defined parameters, and allows you to define the thrown exception type as well.
• ...
• Also take a look at less common use varargs based
          Lambda.RP, Lambda.RPE, Lambda.RO, Lambda.ROE, Lambda.OO, Lambda.OOE
        Lambda.VP, Lambda.VPE, Lambda.VO, Lambda.VOE
  which are commented in the source code of Lambda.java.

With this library you can also safely:

• Go from Lambda.R1E to a Lambda.V1E by simply calling lambda.V1E() where we ignore making use of the return value for the desired void lambda.
• Go from Lambda.V1E to a Lambda.R1E by also simply calling lambda.R1E() but comes with a small caveat where we return null instead which is fine as long as the invoker of the lambda.call() handles return null properly.
• Go from R to R1, R1E, R2, R2E, R3, R3E, R4, R4E, R5, R5E by simply calling the method with the same name, such as lambda.R4E().
• ...

Documentation is provided through comments within the class itself and we recommend you start try to use it, and you will immediately figure out its use.

• Nice compact, partial view over signatures from Intellij over Lambda.java:

  

Examples

• examples/IO.java

  

• examples/Lists.java

  

Recommendation

• Since a Lambda.V extends Lambda.VE<RuntimeException>, Lambda.R extends Lambda.RE<RuntimeException>, Lambda.V1<P1> extends Lambda.V1E<P1, RuntimeException> we recommend that you always try to use a throw capable Lambda for your declared methods which ultimately depends on intetions like if you want lambda.call() to bubble non RuntimeExceptions or if you want to force the handlement of exception inside the lambda body (think Runnable and Thread)? This way, you have the option to handle any exception in the Lambda body, as well as being able to simply throw it.

  Take the the Runnable interface as an example where you normally, if you say read from a file which would throw an IOException by default you would be forced to handle that exception. However, using the Lambda interface, and calling a method that expects a throw capable Lambda, that lambda will automatically throw E if there are any by the caller of lambda.call().

• For your base methods, try to use an R lambda with E whenever possible, such as Lambda.R[1-5]E. This is versitale and would allow you to add delegating methods of most flavours more easily.

Keep in mind

• A Lambda.R can automatically and safely be converted to to any Lambda.R1 -Lambda.R5 as well as Lambda.V - Lambda.V5 and there are util methods for these things. A Lambda.R5 can not be safely converted to a Lambda.R4 since the body in Lambda.R5 expects 5 params and converting it to Lambda.R4 would leave at least one null.
  To make conversions from Lambda.R5 to Lambda.R4 or Lambda.V4 you would have to do it manually.

  On a similar note, Lambda.V1 can be converted to a Lambda.R1 and there are util methods for that. This is achieved by simply returning null, which is always possible even when supplying a Lambda.R1 to begin with. Therefore the lambda.call() should handle return null.

• Whenever possible, the interfaces implement equivalent interfaces such as Runnable, Consumer, BiConsumer, Function, BiFunction, Supplier and can thus be used and fed to methods expecting those allowing you to stick with using this consistent naming pattern.

  As an example, Lambda.V extends Runnable with run() implemented to delegate to call(), Lambda.R<R> extends Supplier<R> with get() implemented to delegate to return call(), Lambda.R1<R,P> extends Function<P, R>with apply(P param) implemented to delegate to return call(param) and so forth. This means you can opt to supply a Lambda.V to anything that accepts a Runnable, Lambda.R to anything that accepts a Supplier making it possible to use as a standard for everything.

• We have two namespaces, Lambda and Closure and can be used interoperable. The default namespace is Lambda so you could do Lambda.V1<String>, or Lambda.R1<Boolean, String>. But since the Lambda namespace is sometimes difficult to complete (intellij) due to its wide use, you could instead do Closure.V1.
  Closure.V1 == Lambda.V1, Closure.R2E is the same as Lambda.R2E, it just access to it is provided though another class.

License

The full license can be found here MoL9

Contribute

Send an email to opensource{at}momomo.com if you would like to contribute in any way, make changes or otherwise have thoughts and/or ideas on things to improve.

Pipeline

• Add E[2-5] as well to allow for more defined exception types, in cases where multiple exception types are thrown from Lambda. Normally this would be handled by throwing the least common Exception denominator but this is not always ideal to do.

• Add V[6-10], VE[6-10], R[6-10], RE[6-10] as well to cover all sceptics out there thinking they will ever need more than 5.