exception handling - Java , i keep getting StringIndexOutOfboundsException -

this supposed isolate names , scores , calculate average of scores. output should this:

student name             test 1    test 2    test 3     final   average   susan smith                 76        78        90       100     88.80  susan boyd                 100        88        79        88     88.60  alex chandler               88        99        77        66     79.20  

but keeps throwing stringindexoutofboundsexception. why?

this error:

java.lang.stringindexoutofboundsexception: string index out of range: 0 @ java.lang.string.charat(string.java:646) @ calcweightedaverage.extractname(calcweightedaverage.java:49) @ calcweightedaverage.main(calcweightedaverage.java:30) 

here code:

import java.util.*; //import java.util scanner import java.io.*;// import java io printwriter  /**  * class takes input file scores , outputs scores weighted average  *  * @author  * @version 10/30/2015  */ public class calcweightedaverage {     /**      * method akes input file scores , outputs scores weighted average      *      * @param string args      * @return void      */     public static void main(string[] args) throws filenotfoundexception {         scanner in = new scanner(system.in); // creating scanner read keyboard         system.out.print("please enter name of input file: "); // prompt file name         printwriter out = new printwriter("outputfile.txt"); // declares new printwriter outputfile name         string filename = in.nextline(); // puts user input filename         file infile = new file(filename);//makes new file , puts user input in          scanner in1 = new scanner(infile);// declaring scanner whats in file         out.printf("%-21s%10s%10s%10s%10s%10s", "studentname", "test 1", "test2", "test 3", "final", "average"); // first line in output         out.println(); // go next line         while (in1.hasnextline()) {             string line = in1.nextline(); // new string file             string studentname = extractname(line); // extracts student name using method             double[] studentscore = new double[5]; // new array store values             studentscore = extractvalue(line);// invoke method calculate values             out.printf("%-20s%10.0f%10.0f%10.0f%10.0f%10.2f", studentname, studentscore[0], studentscore[1], studentscore[2], studentscore[3], studentscore[4]); // edit scores             out.println();// next line         }         in.close(); // closes scanner         in1.close();//closes scanner         out.close();//closes printwriter     }       /**      * extracts student name input line.      *      * @param pline line containing student name, followed number      * @return student name      */     public static string extractname(string pline) {         int = 0; // locate start of first digit         while (!(character.isdigit(pline.charat(i)))) {             i++;         }         return pline.substring(0, i).trim(); // extract student name , return     }      /**      * extracts value input line.      *      * @param pline line containing student name, followed value      * @return value associated name      */     public static double[] extractvalue(string pline) {         int = 0; // locate start of first digit         while (!character.isdigit(pline.charat(i))) {             i++;         }         // extract , convert value         string scorestring = pline.substring(i).trim(); // extract score , return         scanner score = new scanner(scorestring); // new scanner score         int testscore1 = score.nextint(); // value of first score         int testscore2 = score.nextint();// value of second score         int testscore3 = score.nextint();// value of third score         int finalscore = score.nextint();// value of final score         double average = testscore1 * 0.2 + testscore2 * 0.2 + testscore3 * 0.2 + finalscore * 0.4; // calculates weighted average         double[] result = new double[5];// new array input         result[0] = testscore1;// value of first score         result[1] = testscore2;// value of second score         result[2] = testscore3;// value of third score         result[3] = finalscore;//value of final score         result[4] = average; // value of average         return result;// return average     } } 

the problem in input file has have few spaces otherwise doesnt work