Declaring Loop Control Variables Inside the for

Concept

• It is possible to declare the control variable directly in the for loop declaration.
• This is useful when the variable is only needed within the loop itself.

Advantages

• Improves code readability and organization.
• Limits the scope of the variable to the loop, reducing the possibility of errors.

Example

• The following program calculates the sum and factorial of the numbers from 1 to 5, declaring the control variable i inside the for:

// Declara a variável de controle de laço dentro de for.
class ForVar {
    public static void main(String args[]) {
        int sum = 0;
        int fact = 1;
        // calcula o fatorial dos números até 5
        for(int i = 1; i <= 5; i++) {
            sum += i; // i é conhecida em todo o laço
            fact *= i;
        }
        // mas não é conhecida aqui
        System.out.println("Sum is " + sum);
        System.out.println("Factorial is " + fact);
    }
}

Important
The scope of the variable declared within the for is limited to the loop.
Outside the for, the variable is not accessible:

// Declaração correta dentro do for
for (int i = 0; i < 5; i++) {
    System.out.println(i); // i é acessível aqui
}
// System.out.println(i); // Erro: i não é conhecida fora do laço

Use and Limitations

Declare the variable inside the for when it is not needed outside the loop.
If you need to use the variable outside the loop, declare it before for:

int i; // Declarada fora do laço
for (i = 0; i < 5; i++) {
    System.out.println(i);
}
// i é acessível aqui
System.out.println("Final value of i: " + i);

Exploration

Test variations of the for loop to better understand its flexibility and behavior.

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