Comparison of C Sharp and Java: Difference between revisions

Revision as of 23:20, 4 February 2010

Revision as of 18:06, 5 February 2010

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A common reason for using try-finally blocks is to guard resource managing code, so that precious resources are guaranteed to be released in the finally block. C# features the <code>using</code> statement as a syntactic shorthand for this common scenario, in which the <code>Dispose()</code> method of the object of the <code>using</code> is always called.

==== Finally Blocks and Uncaught Exceptions ====

Java allows flow of control to leave the <code>finally</code> block of a <code>try</code> statement, regardless of the way it was entered. This can cause another control flow statement (such as <code>return</code>) to be terminated mid-execution. For example:

Both C# and Java handle execution of finally blocks exactly the same when dealing with an uncaught exception.

<ref>try

<source lang="java">

{

int foo() {

Console.Out.WriteLine("In Try");

try {

throw new Exception();

return }0;

} finally {

finally

return {1;

}

Console.Out.WriteLine("In Finally");

}

}</ref>

</source>

In the above code, the <code>return</code> statement within <code>try</code> block causes control to leave it, and therefore <code>finally</code> block is executed before the actual return happens. However, <code>finally</code> block itself performs a return as well; thus, the original return that caused it to be entered is not actually executed, and the above method returns 1 rather than 0.

In C#, no statements which allow control flow to prematurely leave the <code>finally</code> block are allowed, except for <code>throw</code>. In particular, <code>return</code> is not allowed at all, <code>goto</code> is not allowed if the target label is outside the <code>finally</code> block, and <code>continue</code> and <code>break</code> are not allowed if the nearest enclosing loop is outside the <code>finally</code> block.

=== Lower level code ===