Import Libcore. Io. Disklrucache Failed

I want to use DiskLruCache in my project as explained in Caching Bitmaps, but cannot import the correct lib.

Where can I find the jar containing this class ?

As suggested in similar questions, I added the following line to my build.gradle :

dependencies {
    ...
    compile 'org.robovm:robovm-rt:+'
}

Gradle seems to find the lib, but my code still does not compile :

package com.example ;

import android.util.LruCache;

import libcore.io.DiskLruCache;

public class ObjectCache {

    private LruCache<String, String> memoryCache;
    private DiskLruCache diskLruCache ;

    public ObjectCache(int cacheSize) {
        memoryCache = new LruCache<String, String>(cacheSize);
        diskLruCache = null ;
    }
}

It fails with following errors :

Error:(5, 18) error: package libcore.io does not exist
Error:(10, 13) error: cannot find symbol class DiskLruCache