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for loop instantiation fail to compile?
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A: If you declare a variable in a for loop without braces the Sun compiler will fail with the message "not a statement", but the message is misleading. A more appropriate error message would be "o is already defined". In this case there is no contained scope for the variable o, so every pass through the loop would have the effect of declaring the variable again and again.
// Does not compile for ( ; ; ) Out o = new Out();
Without braces its as if you had written a continuous list of variable declarations:
// Does not compile Out o = new Out(); Out o = new Out(); ...
In the example below the for loop statement is enclosed in curly braces, which gives the variable declaration more precise scope. In this case, each pass through the loop creates a "throw-away" variable which is local to the statement block.
for ( ; ; ) { // Compiles Out o = new Out(); }
This question is not particularly to do with the for loop and it makes no difference whether the loop runs once or an infinite number of times. The significant point is not to do with assignment, it is about the declaration of the variable and the scope the variable has. The annotated example below continues the case of the for loop, but the key is to compare the different syntax that follows the for conditions.
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Why does this for loop instantiation fail to compile?
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