这个为什么会无限循环！

public class Solution {
public static void main(String[] args) throws Exception {
Scanner sc = new Scanner(System.in);
int a = sc.nextInt();
int i = 0;
while(a!=-1){
i=i+a;
}
while(a==-1){
int j =i-1;
System.out.println(j);

}
 }
}