Final keyword and using instances of an interface

[JProg]

Hi Everyone,

I have been studying a book on multi-threading and have inadvertently come accross some code that I don't really understand. I am wondering if anybody can explain to me the following:
1). What effect does using the final keyword have when instantiating objects, and
2). How is it possible to instantiate an object from an interface?

public class BothInMethod extends Object
{
private String objID;

public BothInMethod(String objID)
{
this.objID = objID;
}

public void doStuff(int val)
{
print("entering doStuff()");
int num = val * 2 + objID.length();
print("in doStuff() - local variable num=" + num);

// slow things down to make observations

try{
Thread.sleep(2000);
}catch(InterruptedException x){}

print("leaving doStuff()");
}

public void print(String msg)
{
String threadName = Thread.currentThread().getName();
System.out.println(threadName + ": " + msg);
}

public static void main(String[] args)
{
final BothInMethod bim = new BothInMethod("obj1");

Runnable runA = new Runnable()
{
public void run()
{
bim.doStuff(3);
}
};

Thread threadA = new Thread(runA, "threadA");
threadA.start();

try{
Thread.sleep(200);
}catch(InterruptedException x){}

Runnable runB = new Runnable()
{
public void run()
{
bim.doStuff(7);
}
};

Thread threadB = new Thread(runB, "threadB");
threadB.start();
}
}

If you know of any good tutorials that explain this (preferably URL's) then please let me know. Thanks heaps for your help.

Regards

Davo

 

[sedj]

final means final. The object must be either specified in the declaration, or in the constructor.

interfaces explained :

http://java.sun.com/docs/books/tutorial/java/interpack/interfaces.html

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[Diancecht]

And cannot be re-especified, btw.

For methods, it means that subclasses cannot override it

Cheers.

Dian.