This project has been abandoned.
The provided Strings-functions can be used from the Kotlin standard-library, thanks to Kotlin's Java interoperability
even from Java apps. And the Preconditions aren't worth an extra library project.
However, since android-utils is still available via jcenter, the code will remain here and stay open-source.
android-utils is a library for Android apps to provide some convenient utility-functions that are not part of the java8 standard-library or are neither usable in your app due to API level constraints nor backported in streamsupport.
Make sure you have 'jcenter' added to your repositories in your build.gradle file:
allprojects {
    repositories {
        jcenter()
    }
}
Then add android-utils to your dependencies:
dependencies {
    implementation 'rocks.frieler.android:android-utils:0.5.0'
}
Now you can use the features briefly explained below:
rocks.frieler.android.utils.Strings contains all kind of utility-functions dealing with Strings.
rocks.frieler.android.utils.Preconditions contains utility-functions to check the preconditions of functions.