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Final modifier in enhanced for-loop : How can this be?

Sandra Bachan
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Joined: Feb 18, 2010
Posts: 434
Enthuware question:

Identify the valid for loop constructs assuming the following declarations:



We have to select two options

1. for(o : c){ }
2. for(final Object o2 :c){ }
3. for(int i : ia) { }
4. for(Iterator it : c.iterator()){ }
5. for(int i : ia[0]){ }


I can understand how option 5 is correct; ia is an array of arrays, and the enhanced for-loop can traverse ia[0], which holds an array

How is option 2 correct? I thought that final in front of reference variable Object o2 means that once it points to an object on the heap, it does NOT point to ANOTHER object, otherwise you get compiler error. Yet, by traversing collection c, final Object o2 is pointing to DIFFERENT objects in the collection.

Please explain.


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Henry Wong
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Joined: Sep 28, 2004
Posts: 18553
    
  40

Sandra Bachan wrote:
How is option 2 correct? I thought that final in front of reference variable Object o2 means that once it points to an object on the heap, it does NOT point to ANOTHER object, otherwise you get compiler error. Yet, by traversing collection c, final Object o2 is pointing to DIFFERENT objects in the collection.

Please explain.


The final keyword, when it is used to specify the loop variable of the enhanced for-loop, means that the variable can't be changed during each iteration of loop.

Henry


Books: Java Threads, 3rd Edition, Jini in a Nutshell, and Java Gems (contributor)
 
 
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