Greetings...I'm new to Java and the P2P site.

I have a question on the "Calculating Primes" examples in chapter 3 used to illustrate loops using the "break" and "continue" statements. I mostly understand the logic of the code and how it chooses to display a number as being prime or not except for the number 2 (which i know is a prime number). However I don't quite understand how the number 2 is allowed to be displayed.

When the IF statement in the inner FOR loop is executed the first time both "i" and "j" have a value of "2". If both have a value of 2 then the remainder of "j" dividing "i" is zero and the IF statement should evaluate to TRUE, which in turn means the variable "isPrime" is assigned a value of FALSE and the BREAK statement is executed. When the IF statement in the outer loop is executed "isPrime" now has a value of FALSE which means the println statement should not execute and display the value of "i" when it equals "2".

After the completion of the first iteration of the outer FOR loop and "i" is incremented to 3, I understand how all prime numbers from there on (up to 50) are displayed. Again, my problem is when both "i" and "j" equal 2.

Please help me understand where my thinking/logic is wrong :)

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Update:
Here's the code for the example I'm referring to:
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public class Primes {
public static void main(String[] args) {
int nValues = 50;
boolean isPrime = true;
for(int i = 2; i <= nValues; ++i) {
isPrime=true;
for(int j = 2; j < i; ++j) {
if(i % j == 0) {
isPrime = false;
break;
}
}
if(isPrime)
System.out.println(i);
}
}

}

When both i and j equal 2, the inner loop simply doesn't execute at all. Look at its testing condition, in bold:
for (int j = 2; j < i; ++j) {...}
So you get 2 < 2, which is false, therefore the loop doesn't even begin to execute. The logic immediately skips to this line:
if (isPrime)
which happens to be true at that time, so the program prints "i", i.e. 2.

Awesome! Thanks sklm!!

Now it makes sense!!!! Based on what you are saying the testing condition is evaluated BEFORE the loop begins. If it evaluates to false then the loop never starts and it bypassed, if it evaluates to true then the loop begins and the testing condition is evaluated once for each iteration of the loop.

I thought that the loop executes at least once first then checks the testing condition to see if it should continue.

Here's what the book says when describing FOR loops:

"Execution of this loop continues as long as the condition you specify in the second part of the control mechanism, the loop_condition, is true. This expression is checked at the beginning of each loop iteration, and as long as it is true, the loop body executes."

After your explanation I guess I can see more of what they meant but for me it would have been clearer if they would have said: "Execution of this loop starts and continues as long as the condition you specify in the second part......"

Thanks again!

That explanation really helped a lot!!

Not the For loop. But there is the Do-While loop that does exactly that.