Holliday Java Quiz: ConcurrentModificationException

Tomorrow is Thanksgiving in the US. And here is a little Java quiz that you may want to ponder on while the turkey is in the oven. (BTW, I just recently realized I've been pronouncing the word 'oven' wrong all these years. Apparently it's not [oh-vn], but [uh-vn].)

Q: For the following Foo.java, is it ever possible for line 21 to throw a java.util.ConcurrentModificationException?

1    import java.util.ArrayList; 
2    import java.util.List; 
3     
4    public class Foo { 
5      private final List<Bar> bars = new ArrayList<Bar>(); 
6     
7      public void add(Bar bar) { 
8        synchronized(bars) { 
9          bars.add(bar); 
10       } 
11     } 
12    
13     public void remove(Bar bar) { 
14       synchronized(bars) { 
15         bars.remove(bar); 
16       } 
17     } 
18    
19     public void close() { 
20       synchronized(bars) { 
21         for (Bar bar: bars) { 
22           bar.close(); 
23         } 
24         bars.clear(); 
25       } 
26     } 
27   }

Have a happy Thanksgiving.

Responses[7]

Posted by Weiqi Gao on November 26, 2008 12:21:44 PM CST #