Java substring difficulty -

i know how use substring() why isn't working, user inputs equation "5t + 1" space before , after "+". want tvariable hold integer before it, in case 5 , constant should hold constant integer in case 1, out of range error.

import java.util.*; import javax.swing.joptionpane;  public class project3030  {         public static void main(string[] args) {         string l1x, tvariable, constant;         l1x = joptionpane.showinputdialog("this format (x=5t + 1)");          int endindex = l1x.indexof("t");          tvariable = l1x.substring(0, endindex);          int beginindex = l1x.lastindexof(" ");         int endindex2 = l1x.indexof("");                      constant = l1x.substring(beginindex, endindex2);          system.out.println(tvariable + constant);     } } 

you need change more like

constant = l1x.substring(l1x.lastindexof(" ")).trim(); 

then when add numbers, have parse them before add them.

int constantint = integer.parseint(constant); 

or use solution:

string[] input = l1x.split(" ");   // remove 't' string tnum = input[0].substring(0, input[0].length() - 1); int t = integer.parseint(tnum);  int constant = integer.parseint(input[2]);  string operator = input[1];  if (operator == "-")     constant *= -1;