java 编程

我想我输入一个字个阵 分到 r 出先 定系n出先 我条code应该点改
import java.util.Scanner;

public class Lab {

public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String str;
char chk;
int x = -1;
int y = -1;
boolean a = true, b = false;
System.out.println("Please input a string");
str = input.next();
for (int i = 0; i < str.length(); i++) {
chk = str.charAt(i);
if (chk == 'r')
x = i;
if (chk == 'n')
y = i;
if ((y > x) && (y != 0))
System.out.println("N " + y);
else if ((y < x) && (x != 0))
System.out.println("R " + x);
else
System.out.println("not");
}
}
}

for (int i = 0; i < str.length(); i++) {
chk = str.charAt(i);
if (chk == 'r')
x = i;
if (chk == 'n')
y = i;

has problem. if the string has more then one r or y. the x and y will become the last char number.
If you want to show 1st r and 1st y in string, you need to add "break" after x=i and y =1; The break will stop the for loop.