flag Using boolean in Java

In Java programming, a flag is often a boolean variable (true or false) used to track or control the flow of logic in loops and conditions.

It's like raising a "red flag" to say something happened.

What is a Flag?

A flag is a temporary indicator.

It’s usually declared like this:

boolean flag = true; // or false

We change this flag based on a condition, then check its value after a loop or block to decide what to do next.

STRUCTURE:

// 1. Declare and initialize
boolean flag = true; // or false

// 2. Run your loop or logic
while (condition) {
if (someConditionIsMet) {
flag = false; // or true
break;
}
}

// 3. Use the flag in if-else
if (flag) {
// Do something if the flag is true
} else {
// Do something else if the flag is false
}

exapmle :

public class PrimeChecker {
public static void main(String[] args) {
int num = 29;
int i = 2;
boolean flag = true; // Assume prime

    while (i <= num / 2) {
        if (num % i == 0) {
            flag = false; // Found a factor, not prime
            break;
        }
        i++;
    }

    if (flag && num > 1) {
        System.out.println(num + " is a prime number");
    } else {
        System.out.println(num + " is not a prime number");
    }
}

}

output :

29 is a prime number

reference link:
1: https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html

2: https://docs.oracle.com/javase/tutorial/java/nutsandbolts/while.html