All three aspects of the loop
are done in one statement. This makes it easier to check if you have done things correctly.
Here is a counting loop:
int count; . . . . . . for ( count = 0; count < 10; count++ ) System.out.print( count + " " );
The loop control variable
count has been declared somewhere in
the program, possibly many statements away from the
This violates the idea that all the parts of the loop are combined in one statement.
It would be nice if the declaration of
count were part of the
this can be done, as in the following:
for ( int count = 0; count < 10; count++ ) System.out.print( count + " " );
In this example, the declaration of
count and its initialization
have been combined.
However, there is an important difference between this program fragment and the previous one:
Scope Rule: a variable declared in a
forstatement can only be used in that statement and the body of the loop.
The following is NOT correct:
for ( int count = 0; count < 10; count++ ) System.out.print( count + " " ); // NOT part of the loop body System.out.println( "\nAfter the loop count is: " + count );
println() statement is not part of the loop body,
count cannot be used here.
The compiler will complain that it "cannot find the symbol: count"
when it sees this
This can be a baffling error message if you forget the scope rule.
Is the following code fragment correct?
int sum = 0; for ( int j = 0; j < 8; j++ ) sum = sum + j; System.out.println( "The sum is: " + sum );