Help! Converting JavaScript to Java

Question

I know I am going to get laughed at for this, but as you can probably tell my knowledge of Java is poor at best.
Years ago, I wrote the following code in JavaScript:
function overImg(imageName)
    if (version == "java")
        imageOn = eval(imageName + "roll.src");
        document [imageName].src = imageOn;
}Question is, how can I recreate something similar in Java?
The key part is that the code allows me to use a reference to an object rather than the object itself. How can I do that in Java?
If this question seems stupid then feel free to tell me so. I freely admit my knowledge of Java is not good.
Thank you in advance,
G

Answer 1

If I had a search method, how can I pass the book object to the method >if I don't know what the object will be called when I compile?Something like this...
Library.java
private List bookList;
public boolean search(Book b){
    String isbn = b.getISBN();
    return bookList.contains(isbn);
public void addBook(Book b){
    bookList.add(b.getISBN());
Library.java
public String getISBN(){
   //return an isbn for this book