The For Loop

We would like to :

Here is a tutorial/reference.
Remember to have a successful loop we must
1. Initialize the loop control variable.
2. Have a test on the loop control variable that will become false.
3. Change the loop control variable to make progress.
Often when I write a while loop I forget to do one of these.
- And I am not alone.

So most languages provide a for loop.

Syntax:

for (initialize statement; boolean expression; increment statement)
     body statement;

Semantics

initialize statement
while (boolean expression) {
     body statement;
     increment statement;
}

Use:

for (initialize statement; boolean expression; increment statement) {
    body statements;
}

In the last program I replaced

i = 0;
while (i < dataParts.length) {
     System.out.printf("Part %d is '%s'\n",i, dataParts[i]);
     ++i;
}

With:

for (i = 0; i < dataItems.length; ++i) {
      System.out.printf("Item %d is '%s'\n",i, dataItems[i]);
}

When to use a for loop:
- In theory you could use one for everything.
- But I tend to say use them when you "know" how many iterations you will perform (counter controlled loops)
The for loop is my go to loop because it reminds me to do all the parts.
For loops are ideal for array processing.
I will use for loops from here on out when appropriate.
Declaring the loop control variable
- A modern approach is to not declare variables until you need them.
- This started with loops.
- ```
for(int i = 0; i < dataItems.length; ++i) {
} 
```
- I tend to like this and have started using it.
- But if your other instructor says NO, don't do it.
- The only problem is that i is not accessible outside the loop.
  - This is a scoping rule we will talk about later.