java - Infinite loop when trying to read and create a file -

this java code compiles. when ran program, lasted long time , didn't results, , said runofoutspace, guess fell infinite loop, cannot figure out why.

import java.util.*; import java.io.*; public class exercise3{ public static void main (string[] args){ file infile = new file(args[0]); file outfile = new file("ex3.txt"); try {   scanner scan = new scanner(infile);   arraylist<string> readfile = new arraylist<string>();   string findword = args[1];   string replaceword = args[2];    while(scan.hasnextline())   {     readfile.add(scan.nextline());   }   //system.out.println(readfile);   (int i=0; i<readfile.size();i++)   {     string n = readfile.get(i);     n = n.replaceall(findword,replaceword);     readfile.add(i,n);   }    printwriter output = new printwriter(outfile);   (int i=0; i<readfile.size();i++)   {     output.println(readfile.get(i));   }   output.close();   scan.close(); } catch (filenotfoundexception e){   system.err.println("file not found."); }     } } 

the issue :

  (int i=0; i<readfile.size();i++)   {     string n = readfile.get(i);     n = n.replaceall(findword,replaceword);     readfile.add(i,n);   } 

you incrementing size of arraylist, inside for-loop. readfile.add(i,n); . size of readfile gets incremented on each iteration of loop, loop condition never evaluate false.

when add new element @ index i, former element @ index shifted right. won't replaced.