You could use Google Translate API, but it's a paid service.
I recommend you have a look at Microsoft's Bing Translate API, which is free (up to a character limit)
You can check MS's translator out here:
http://www.microsoft.com/en-us/translator/developers.aspx[
^]
I'm not familiar with native Java/Android development, but you could build your app with web technologies if they integrate with the translation API better. I've written
an article here on CP that demonstrates how a semi-native Android app can be made with Web Technologies.