DataObjects.java

public class Book implements Literature {
    // variables and methods

    @Override
    public int getType() {
        return Literature.TYPE_BOOK;
    }
}

public class Magazine implements Literature{
    // variables and methods

    @Override
    public int getType() {
        return Literature.TYPE_MAGAZINE;
    }
}

public class Newspaper implements Literature {
    // variables and methods

    @Override
    public int getType() {
        return Literature.TYPE_NEWSPAPER;
    }
}