For some reason, DiskLruCacheTest.java runs fine, but Main.java hangs before returning and doesn't write to the cache. EDIT: Fixed the issue by using Math.pow() instead of ^.

DiskLruCacheTest.java

import junit.framework.Assert;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.*;
import java.util.ArrayList;
import java.util.List;

public class DiskLruCacheTest {

    @Test
    public void testStoreArrayList() throws IOException {
        // fixed: changed from 20 * 2^20 to (long) (20 * Math.pow(2, 20))
        DiskLruCache diskLruCache = DiskLruCache.open(new File("DiskLruCacheTest"), 1, 1, (long) (20 * Math.pow(2, 20)));

        DiskLruCache.Editor editor = diskLruCache.edit("test-store-array-list");
        OutputStream os = editor.newOutputStream(0);
        OutputStream bos = new BufferedOutputStream(os);
        ObjectOutputStream oos = new ObjectOutputStream(bos);

        List<String> list = new ArrayList<String>();
        list.add("first string");
        list.add("second string");

        oos.writeObject(list);

        oos.close();
        editor.commit();

        diskLruCache.close();
    }
}

Main.java

import java.io.*;
import java.util.ArrayList;
import java.util.List;

public class Main {

    public static void main(String[] args) throws IOException {
        // fixed: changed from 20 * 2^20 to (long) (20 * Math.pow(2, 20))
        DiskLruCache diskLruCache = DiskLruCache.open(new File("DiskLruCache"), 1, 1, (long) (20 * Math.pow(2, 20)));

        DiskLruCache.Editor editor = diskLruCache.edit("test-store-array-list");
        OutputStream os = editor.newOutputStream(0);
        OutputStream bos = new BufferedOutputStream(os);
        ObjectOutputStream oos = new ObjectOutputStream(bos);

        List<String> list = new ArrayList<String>();
        list.add("first string");
        list.add("second string");

        oos.writeObject(list);

        oos.close();
        editor.commit();

        diskLruCache.close();
    }

}