memoizr / retro-optional Goto Github PK

A backport of Java8 monad optionals for Java7.

Example: Let's say we have an instance of a class A which can be nullable, and we're interested in getting the result of a chain of nested function calls, which eventually will result in a boolean. Every intermediate step may fail and return a null. To get to the end result without optionals we'd have to do multiple null checks:

boolean result = a != null &&
      a.getB() != null &&
      a.getB().getC() != null &&
      a.getB().getC().isD();

But by converting everything to return monadic optionals, the syntax can be streamlined a bit:

boolean result = a.flatMap(A::getB)
      .flatMap(A::getC)
      .filter(x -> x.isD())
      .isPresent();

For more examples of how to use Java 8 optional types, you can refer to this excellent article: http://www.nurkiewicz.com/2013/08/optional-in-java-8-cheat-sheet.html

 repositories {
        // ...
        maven { url "https://jitpack.io" }
  }

 dependencies {
        compile 'com.github.memoizr:retro-optional:0.2.0'
  }

Copyright 2015 memoizr

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
implied.
See the License for the specific language governing permissions and
limitations under the License.