Exception in thread “main” java.lang.ArrayIndexOutOfBoundsException: 160 [duplicate]

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This question already has answers here:

What causes a java.lang.ArrayIndexOutOfBoundsException and how do I prevent it? (25 answers)

Closed 2 years ago.

This code is basically adding binary numbers. For some reason I keep getting an index out of bounds error on line 102 which is the nested for loop if statement towards the bottom. Can anyone guide me in the right direction?

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class Process {

  private String storeString="", x="";
  private String polynomial;

  //get file 
  public void getFileName(String fileName) {                        
    try (BufferedReader br = new BufferedReader(new FileReader(fileName))) { 
      String sCurrentLine="";

      while ((sCurrentLine = br.readLine()) != null) {  
        storeString+= sCurrentLine.toUpperCase();
      }
    } 
    catch (IOException e) {
      System.out.println("Sorry no such file is was found!" +
                         "\n\nAre you sure that's the right file name");
    }   
    System.out.println(storeString);

    if (storeString.matches("[0-9A-F]+") == true) {
      System.out.println("true");
      hexToBin(storeString);
    } else {
      System.out.println("Sorry that is an Invalid Hex");
      System.exit(0);
    }       
    System.out.println(x);

  }

  //convert to binary       
  public void hexToBin(String hex) {
    String bin = "";
    String binFragment = "";
    int iHex;
    hex = hex.trim();
    hex = hex.replaceFirst("0x", "");

    for (int i = 0; i < hex.length(); i++) {
      iHex = Integer.parseInt(""+hex.charAt(i),16);
      binFragment = Integer.toBinaryString(iHex);

      while (binFragment.length() < 4) {
        binFragment = "0" + binFragment;
      }
      bin += binFragment;
    }
    System.out.println("length:" + bin.length());
    Calculate(bin.length(), bin);
  }

  // calculations
  public void Calculate(int size, String hex) {
    char [] poly= new char[17];
    char [] charBin= new char[size];
    int move=-1,zero=0,L=0;

    polynomial = "10000100110001101";

    //convert to char
    for (int i=0; i < 17; i++) {
      poly[i] = polynomial.charAt(i);
    }
    //convert hex to char
    for (int i=0; i < size; i++) {
      charBin[i] = hex.charAt(i);
    }

    //compare with if statements
    for (int i=0; i < size ; i++) {
      for(int j=0; j < 17; j++) {
        move++;
        if (charBin[move]=='1' && poly[j]=='1') {
          charBin[move] = '0';
        } else if (charBin[move]=='0' && poly[j]=='0') {
          charBin[move] = '0';
        } else {
          charBin[move] = '1';
        }
      }

      int k=0;
      //print charbin
      //while (charBin[k]!= size) {
      //  System.out.print(charBin[k]);
      //  k++;
      //}

    }//end class

  }//end class

}

Answer 1

Since you loop i up to size and j up to 17 and increment move each time, you can expect move to get up to 17 * size - 1. You are using it to index into an array of length equal to size.

char[] charBin = new char[size];
int move = -1;
...
for(int i=0;i < size ; i++) {
   for(int j=0;j < 17;j++) {
      move++;
      if(charBin[move]) ...
   }
}

Answer 2

charBin has size locations. But you are accessing its values in your loop using move as an index. move is being incremented every time inside your second loop:

char[] charBin = new char[size];
int move = -1;
for(int i=0;i < size ; i++) {
    ...
    for(int j=0;j < 17;j++) {
        ...
        move++;
    }
}

In the outer loop i runs from 0 to size and in the inner loop j runs from 0 to 17. move therefore has a potential maximum value of size * 17. As soon as move becomes the same value as size, you will get an exception since you are outside the bounds of the array (valid locations in charBin run from 0 to size - 1).