package org.stepic.droid.storage.structure;

public class DbStructureLastStep extends DatabaseInfo {
    public static final String LAST_STEPS = "last_steps";

    public static final class Column {
        public static final String COURSE_ID = "course_id";
        public static final String UNIT_ID = "unit_id";
        public static final String STEP_ID = "step_id";
    }
}

package org.stepic.droid.storage.structure;

public final class DbStructureLastStep {
    public static final String LAST_STEPS = "last_steps";

    public static final class Column {
        public static final String COURSE_ID = "course_id";
        public static final String UNIT_ID = "unit_id";
        public static final String STEP_ID = "step_id";
    }
}

make dbStructureLastStep final and remove extending form base class