格林模拟试题二(下)(4)

 question 40)

which of the following statements are correct?

1) if multiple listeners are added to a component only events for the last listener added will be processed
3) adding multiple listeners to a comnponent will cause a compile time error

 

question 41)

given the following code

class base{}
static boolean b1=false;
static double d = 10.1;
mycast m = new mycast();
//here
}
which of the following, if inserted at the comment //here will allow the code to compile and run without error

1) b=m;
3) d =i;

 

question 42)

which of the following statements about threading are true

1) you can only obtain a mutually exclusive lock on methods in a class that extends thread or implements runnable
3) a thread can obtain a mutually exclusive lock on an object by calling a synchronized method on that object.

 

question 43)

your chief software designer has shown you a sketch of the new computer parts system she is about to create. at the top of the hierarchy is a class called computer and under this are two child classes. one is called linuxpc and one is called windowspc.

the main difference between the two is that one runs the linux operating system and the other runs the windows system (of course another difference is that one needs constant re-booting and the other runs reliably). under the windowspc are two sub classes one called server and one called workstation. how might you appraise your designers work?

2) ask for a re-design of the hierarchy with changing the operating system to a field rather than class type
4) change the hierarchy to remove the need for the superfluous computer class