A null aware monadic maybe type in idiomatic Java.

Managing code that handles optional values is often complex and cumbersome.

Prior to Java 8, optional values were usually represented using null values. For example Map.get(K key) returns a null if there is no mapping for the requested key. But null values can also be valid return types. For example from maps which support null values.

As we all know writing code that handles (or forgets to handle) null cases is an incredibly common source of errors.

To address the issue Java 8 introduced the Optional class which can hold either a single non-null value or nothing at all. So what's the problem?

Using Optional effectively removes null from a language where null values can explicitly represent valid parameters and return types.

Maybe is a null aware monad. Meaning unlike Optional it does not use null to signify the absence of a value.

Do yourself a favor and start writing code like this:

 final Maybe<String> maybe = ...
 
 ...
 
 final String value = maybe.ifNull(() -> logger.fine("value is null"))
 .ifNotNull(t -> logger.fine("value is %s", t))
 .ifAbsent(() -> logger.fine("value is absent: using default value"))
 .orElse(DEFAULT_VALUE);

The latest API documentation can be accessed here.