{"id":20863345,"url":"https://github.com/howardabrams/fp-for-java","last_synced_at":"2026-04-28T07:31:02.642Z","repository":{"id":4443179,"uuid":"5581538","full_name":"howardabrams/fp-for-java","owner":"howardabrams","description":"Demonstrating some functional programming principles in Java... it isn't as bad as you'd think (but still not nice)","archived":false,"fork":false,"pushed_at":"2012-10-14T01:08:51.000Z","size":180,"stargazers_count":0,"open_issues_count":0,"forks_count":0,"subscribers_count":1,"default_branch":"master","last_synced_at":"2025-12-29T00:08:55.852Z","etag":null,"topics":[],"latest_commit_sha":null,"homepage":null,"language":"Java","has_issues":true,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":"apache-2.0","status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/howardabrams.png","metadata":{"files":{"readme":"README.md","changelog":null,"contributing":null,"funding":null,"license":"LICENSE-2.0","code_of_conduct":null,"threat_model":null,"audit":null,"citation":null,"codeowners":null,"security":null,"support":null}},"created_at":"2012-08-28T06:12:15.000Z","updated_at":"2014-05-25T01:32:09.000Z","dependencies_parsed_at":"2022-06-25T21:04:28.085Z","dependency_job_id":null,"html_url":"https://github.com/howardabrams/fp-for-java","commit_stats":null,"previous_names":[],"tags_count":0,"template":false,"template_full_name":null,"purl":"pkg:github/howardabrams/fp-for-java","repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/howardabrams%2Ffp-for-java","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/howardabrams%2Ffp-for-java/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/howardabrams%2Ffp-for-java/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/howardabrams%2Ffp-for-java/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/howardabrams","download_url":"https://codeload.github.com/howardabrams/fp-for-java/tar.gz/refs/heads/master","sbom_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/howardabrams%2Ffp-for-java/sbom","scorecard":null,"host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":286080680,"owners_count":32371261,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2026-04-27T20:07:02.737Z","status":"online","status_checked_at":"2026-04-28T02:00:07.250Z","response_time":56,"last_error":null,"robots_txt_status":"success","robots_txt_updated_at":"2025-07-24T06:49:26.215Z","robots_txt_url":"https://github.com/robots.txt","online":true,"can_crawl_api":true,"host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":[],"created_at":"2024-11-18T05:28:37.093Z","updated_at":"2026-04-28T07:31:02.622Z","avatar_url":"https://github.com/howardabrams.png","language":"Java","funding_links":[],"categories":[],"sub_categories":[],"readme":"Function Programming Ideas for Java\n===================================\n\nThe source code in this project (and its accompanying presentation)\ndemonstrate some principles of *functional programming* using standard\nJava.\n\nThe concepts fall into the following categories:\n\nOptional Parameters\n-------------------\n\nIn order to get rid of the dreaded null pointer exceptions, you can\nhave a function accept parameters of type [Option][]. Only two classes\nimplement this interface: `None` and `Some`.\n\n * [None][]: returns `false` when `isPresent()` function is called.\n * [Some][]: returns `true` when `isPresent()` called, and returns results from `values()`\n\nWe can then have a function like:\n \n    public FlexiMap( Option\u003cClosure\u003e putfn, Option\u003cClosure\u003e getfn ) {\n      if(putfn.isPresent())\n        onPut = putfn.get();\n      if(getfn.isPresent())\n        onGet = getfn.get();\n      // ...\n    }\n\nThis process makes it less likely to encounter with `null` values.\n\n\nClosures\n--------\n\nThe [Closure][] interface has a single... ahem... function inside:\n\n    Object apply(Object ...objects);\n\nThis allows anonymous inner classes to pass simple functions around.\nOf course, I find the syntax for anonymous inner classes quite icky,\nand prefer to create private inner classes instead:\n\n    private class DefaultValueForNull implements Closure {\n\t    final Object defaultValue;\n    \t\n      public DefaultValueForNull(Object value) {\n        this.defaultValue = value;\n      }\n    \t\n      public Object apply(Object... objects) {\n        if (objects[0] == null)\n          return defaultValue;\n        else\n          return objects[0];\n      }\n    }\n\n\nComposition\n-----------\n\nTo demonstrate the concept of creating specialized versions of a `Map` through\n*composition* (instead of inheritance), we took [these unit tests][1] from\nthe Apache [Commons Functor library][2], but instead of using their libraries,\nwe used our own `Closure` classes (see [these this code][Test]).\nSame principle, different approach.\n\n  [1]: http://svn.apache.org/repos/asf/commons/proper/functor/trunk/src/test/java/org/apache/commons/functor/example/FlexiMapExample.java\n  [2]: http://commons.apache.org/functor/index.html\n  \n  [Closure]: /howardabrams/fp-for-java/blob/master/src/main/java/org/howardism/fpjava/Closure.java\n  [Option]: /howardabrams/fp-for-java/blob/master/src/main/java/org/howardism/fpjava/Option.java\n  [None]: /howardabrams/fp-for-java/blob/master/src/main/java/org/howardism/fpjava/None.java\n  [Some]: /howardabrams/fp-for-java/blob/master/src/main/java/org/howardism/fpjava/Some.java\n  [Test]: /howardabrams/fp-for-java/blob/master/src/test/java/org/howardism/fpjava/FlexiMapTest.java","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fhowardabrams%2Ffp-for-java","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fhowardabrams%2Ffp-for-java","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fhowardabrams%2Ffp-for-java/lists"}