it says "Runtime Error" no such line - please help me to find out problem in this code

import java.util.LinkedList;
import java.util.Scanner;

class GameOfRobots {

static LinkedList<Node> robots_sub_siquence = new LinkedList<Node>();
static int T;
static String s;
static boolean safe = true;
static Scanner mycan = new Scanner(System.in);


public static void main(String[] args) {
	String s2 = "";
	T = mycan.nextInt();
    s2 = mycan.nextLine();	
    
	//System.out.println("T "+T);

	//System.out.println("nextLine");
	while (T != 0) {
		//System.out.print("type string ");
		s = mycan.nextLine();	
		    
		//System.out.println(s);
		

		//System.out.print("T "+"string "+s);
		if (number_of_robots(s) <= 1) {
			System.out.println("safe");
			continue;
		}else {
			
			// CREATE SUB SEQUENCES				
			int start = next_robot(s, 0);
			//System.out.println("start "+start);
			
			while (start < s.length()) {
				int j = next_robot(s, start+1);
				if (j == -1) {
					break;
				}
				
				//System.out.println("j "+j);
				robots_sub_siquence.add(new Node(start, j));
				start = j;
				
			}
			
			//display_sub_siquence(robots_sub_siquence);
			
		}
		
		// CHECKING COLLIDE OR NOT
		for (int i = 0; i < robots_sub_siquence.size(); i++) {
			Node tem = robots_sub_siquence.get(i);
			
			
			
			int a = get_range(s, tem.getI());
			int b = get_range(s, tem.getJ());
			
			//System.out.println("a b : "+a+""+b);
			
			int total_range = (int) a + b;
			int distance = (int) (tem.getJ() - tem.getI());
			
			//System.out.println("range  : "+total_range);
			//System.out.println("distance  : "+distance);
			
			if (total_range >= (distance)) {
				System.out.println("unsafe");
				safe = false;
				break;
			}
		}
		
		
		if (safe) {
			System.out.println("safe");
		}
		
		
		T--;
		robots_sub_siquence.clear();
		safe = true;
		s = null;
		
		//System.out.println("T"+T);
	}
}

/*
 * 4


.2…
.2…2…
1.1.1.
*
*
*/
private static int get_range(String s2, long i) {
// TODO Auto-generated method stub
switch (s2.charAt((int) i)) {
case ‘0’:
return 0;

		case '1':
			return 1;
		case '2':
			return 2;
		case '3':
			return 3;
		case '4':
			return 4;
		case '5':
			return 5;
		case '6':
			return 6;
		case '7':
			return 7;
		case '8':
			return 8;
		case '9':
			return 9;
			
		default:
			break;
		}
	
	return 0;
}

public static int next_robot(String s, int i) {
	for (int j = i; j < s.length(); j++) {
		if (s.charAt(j) != '.') {
			return j;
		}
	}
	return -1;
}

private static Node get_sub_sequence(int start, int end) {
	// TODO Auto-generated method stub
	
	
	return new Node(start, end);
}
private static int skip_dots(String s2, int j) {
	// TODO Auto-generated method stub
	for (int i = j; i < s2.length(); i++) {
		if (s2.charAt(i) != '.' ) {
			return i;
		}
	}
	return -1;
}
@SuppressWarnings("unused")
private static void display_sub_siquence(
		LinkedList<Node> robots_sub_siquence2) {
	// TODO Auto-generated method stub
	for (int i = 0; i < robots_sub_siquence2.size(); i++) {
		System.out.print("i "+robots_sub_siquence2.get(i).getI());
		System.out.print("j "+robots_sub_siquence2.get(i).getJ());
		System.out.println();
	}
	
}
private static int number_of_robots(String s2) {
	// TODO Auto-generated method stub
	int n = 0;
	for (int i = 0; i < s2.length(); i++) {
		if (s.charAt(i) != '.') {
			n++;
		}
	}
	return n;
}

}

class Node {
long i;
long j;

public Node(int i, int j) {
	this.i = i;
	this.j = j;
}

public Node(long l, long m) {
	// TODO Auto-generated constructor stub
	this.i = l;
	this.j = m;
}

public void setI(int i) {
	this.i = i;
}

public void setJ(int j) {
	this.j = j;
}

public long getI() {
	return i;
}
public long getJ() {
	return j;
}

boolean isCollide(Node a){
	return this.i == a.getI() && this.j == a.getJ();
}

public String toString() {
	// TODO Auto-generated method stub
	return "i "+i+" j "+j;
}

}

//