The "GenerateJavaStubs" task failed

Just copying the answer from here:

Try adding this msbuild property in your project that will shorten the file/folder names on the obj directory

<PropertyGroup>
    <UseShortFileNames>True</UseShortFileNames>
</PropertyGroup>

Or this to change the output folder to a one closer to the C:\

<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
    <IntermediateOutputPath>C:\MyFolder\MyProj</IntermediateOutputPath>
</PropertyGroup>

Hope it helps.

Whats the path to the project you are trying to compile?

Windows has a limit on path names so try moving your project to a shorter named path.
For example if you are using the default project path of C:\Users\YourUserName\Documents\VisualStudio2015\Projects\something then maybe copy it to C:\Dev.