1. Made all classes begin with a capital letter. Like you say, nowits obvious whats a field and whats a class!
2. Changed the constructors for the threads, they now look like:
public OpenLockThread(Padlock padlock) {
this.padlock = padlock;
}
There was a small issue with casting still, because I was saying:
public OpenLockThread(Object padlock) {
this.padlock = padlock;
}
But once I told it it should expect a Padlock and not an object, no casting was needed!
3. That boolean field was changed, and it makes the code nice and easy to read.
I have to say, I really enjoy when code reads like normal English prose, its so much easier to understand!!!

this.padlock = (padlock) padlock;

The above is confusing because ‘padlock’ could refer to the class or the variable.

Generally, boolean field names should be a statement, like ‘padlockIsOpen’. This is so they make sense when you use them in an if statement:

if (padlockIsOpen) { stealBike(); }

HTH!