i was trying to write a code for checking a Palindrome number as below

Question

public class PalindromeNumber{

static int n = 939;
static int x = n;
static int a;
static int sum=0;

public static void main(String[]args){
while(n>0){
a = n%10;
sum = (sum*10) + a;
n = n/10;
}

if(sum==x){
System.out.println(x+" is a Palindrome Number.");
}
else{
System.out.println(x+" is not a Palindrome Number.");
}

}
}
but here my confusion is even if i don't give the variable sum the value of 0. it works
meaning int sum = 0; works and int sum; works too.
i meant it works both ways, whether i give sum the value or not it works ...why..

Answer 1

Because the default value of a variable is zero when declared as a class member. Local variables, instead, need initialization.