Something

int tal;
int max = 0;
int min = 0;
int count = 0;
while(tal != 0){
  tal = scan.nextInt();
  if(tal > max) {
  max = tal;
  } else if(tal < min) {
  min = tal;
  } 
  ++count
}
if(count <= 1){
System.out.println("Inget tal");
} else {
System.out.println(max);
System.out.println(min);