As of the latest release - 1.0.5 of web3j, I am publishing Java 1.6 (i.e. Android) compatible releases. The first Android release is available here, and the artefacts are available on JFrog's Bintray and Maven's Nexus repositories:
<dependency> <groupId>org.web3j</groupId> <artifactId>core-android</artifactId> <version>1.0.5</version> </dependency>
The API is nearly identical to the existing API, with one small difference - you need to use a Web3jFactory to create your client instance:
Web3j web3 = Web3jFactory.build(new HttpService()); // defaults to http://localhost:8545/
For further release notes, please head to the 1.0.5-android release page.