Hot cup of Java sir?

FOR loops are a good way of providing iteration in a programming language. While loops can be considered as a more general form of a for loop. They only use condition and rely on the programmer to fill in the blanks. Consider the for loop below-

for (int a=0; a<=10; a = a + 1){
System.out.println(a);
}

Here is the equivalent while loop -

int a=0
while(a<=10){
System.out.println(a);
a = a + 1
}

The major differences have been highlighted in bold. The biggest difference is that while loops only have a condition. In order for the loop to occur the condition must evaluate to true. As soon as it evaluates to false the loop will terminate.

boolean flag = true;
while(flag){
if (flag == true) flag = !flag;
}

Here is a while loop which does not use a counter. It is much more common to use a while loop to when you do not have a counter rather than a for loop. This is mainly as the for loop statement for this would look like this

for(;flag;)

or maybe

for(boolean flag = true; flag;)

If you do not understand this code then look up the section on IF statements! Remember the condition for both for and while (like if) must evaluate to a boolean. So the above code is perfectly valid. You can also skip out parts of a for loop should you wish. The following code will prioduce a infinite loop -

for(;;){
System.out.println("Infinite loop");
}

There are important differences between a WHILE loop and a FOR loop -

WHILE loops require that the counter be initialized to the starting value manually whilst FOR loops do this automatically (as their start value)
WHILE loops will not automatically increment the counter whilst FOR loops will. WHILE loops require some code which, at some point, will terminate the loop. (force the condition to be false)

next do while / repeat until >>

Basics