For loop example

Question

I've had a quick flick through the headers but can't find if this has been posted before, apologies if it has been covered. I have the JDK 1.6.0 and I use TextPad to compile and run Java. The simple example I have in a textbook does not work:
for (int i=10;i=0;i--)
System.out.printlin(i);
If I compile as above, I get:
C:\Fiona\java\FlatBroke.java:8: incompatible types
found : int
required: boolean
          for(int i=10;i=0;i--)
          ^
1 error
Tool completed with exit code 1
BTW, the ^ appears underneath the "=" in the part of the for statement "i=0", it doesn't seem to paste properly here.
If I change the line to for (int i=10;i<0;i--) it compiles OK but running the app, produces no output, ie ignore system.print etc statement.
Help?

Answer 1

for (int i=10;i=0;i--)
System.out.printlin(i);
If I compile as above, I get:
C:\Fiona\java\FlatBroke.java:8: incompatible types
found : int
required: boolean
          for(int i=10;i=0;i--)
          ^
1 errorYou're confusing assignment and equality tests. The middle expression in a for loop should be an expression whose value is a boolean. But in "i=0", the single equals sign means assignment. You're setting i to zero there. The value of an assignment expression is the value assigned -- in this case, an integer.
So the compiler is complaining because the expression should be boolean-valued, but what you gave it is integer-valued.
You probably meant to do "i==0" instead -- but that's wrong anyway, as we'll see...
If I change the line to for (int i=10;i<0;i--) it
compiles OK but running the app, produces no output,
ie ignore system.print etc statement.That's because the loop ends as soon as the expression is false. "i<0" evaluates to true only if i is greater than zero -- but you've just set it to 10, which is greater than zero.
What you probably want to do in this loop, is "i > 0".