單項選擇題

public class A extends Thread { 
A（） { 
setDaemon（true）； 
} 
public void run（） { 
（new B（））.start（）； 
try { 
Thread.sleep（60000）； 
} catch （InterruptedException x） {} 
System.out.println（“A done”）； 
} 
class B extends Thread { 
public void run（） { 
try { 
Thread.sleep（60000）； 
} catch （InterruptedException x） {} 
System.out.println（“B done”）； 
} 
} 
public static void main（String[] args） { 
（new A（））.start（）； 
} 
}  
What is the result？（）  

A. A done
B. B done
C. A done B done
D. B done A done
E. There is no exception that the application will print anything.
F. The application outputs “A done” and “B done”， in no guaranteed order.

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單項選擇題

public class X implements Runnable { 
private int x； 
private int y； 
public static void main（String [] args） { 
X that = new X（）； 
（new Thread（ that ））.start（）； 
（new Thread（ that ））.start（）； 
} 
public void run（） { 
for （；；） { 
synchronized （this） { 
x++； 
y++； 
} 
System.out.println（Thread.currentThread（）.getName（） + 
“x = “ + x + “， y = “ + y）； 
} 
} 
}  
What is the result？（）  

A. Compilation fails.
B. The program prints pairs of values for x and y that might not always be the same on the same line （for example， “x = 2， y = 1”）.
C. The program prints pairs of values for x and y that are always the same on the same line （for example， “x = 1， y = 1”）.    In addition， each value appears only once （for example， “x = 1， y = 1” followed by “x = 2， y = 2”）.    The thread name at the start of the line shows that both threads are executing concurrently.
D. The program prints pairs of values for x and y that are always the same on the same line （for example， “x = 1， y = 1”）.     In addition， each value appears only once （for example， “x = 1， y = 1” followed by “x = 2， y = 2”）.    The thread name at the start of the line shows that only a single thread is actually executing.
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