Array Index out of bound for loop

Question

import java.util.Scanner;


public class Taxi {

    public static void main(String args[]){
        Scanner input = new Scanner(System.in);
        int groups = input.nextInt();
        int counter=0;

        int[] pass = new int[groups];

        for(int i=0; i<groups; i++){
            pass[i] = input.nextInt();
        }

        for(int i=0; i<groups; i++){
            if(pass[i]==4)
                counter++;

            else if(pass[i]+pass[i+1]<=4){
                counter++;
                i++;
            }
            else 
                counter++;
        }

        System.out.println(counter);
    }

}

keep on receiving error:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 5
    at Taxi.main(Taxi.java:21)

please help

This is a perfect time to learn to read error logs and basic debugging, it will save you a lot of time. — Kuba Spatny
– Kuba Spatny, Commented May 28, 2014 at 18:14

rgettman · Accepted Answer · 2014-05-28 18:13:32Z

3

This line appears to be causing the exception:

else if(pass[i]+pass[i+1]<=4){

You're limiting i to be less than groups, which is the size of the array, but then you deliberately run off the end by using i+1.

Check if i is less than one less than groups first.

else if ( (i < groups - 1) && (pass[i]+pass[i+1]<=4)){

answered May 28, 2014 at 18:13

rgettman

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Comments

Karibasappa G C · Accepted Answer · 2014-05-28 18:29:39Z

0

else if(pass[i]+pass[i+1]<=4) line is your killer definitely.

the reason is you are using for loop with i < groups

 for(int i=0; i<groups; i++)

so i+1 goes to equals to groups for the last iteration.

say for example , it the groups size is 5 then for loop becomes

for(int i=0;i<5;i++)

we can have group[0] ... groups[4] max and groups[5] causes array index out of bound exception.

if we check for loop like above then when i goes to 4 then it satisfies for loop check as 4<5 and enters for loop but there you are doing pass[i] -> ok but pass[i+1] will become like pass[5] which definitely causes array index out of bound exception

so check for loop like below

 for(int i=0; i<groups-1; i++)

it will work now even for the last element.

edited May 28, 2014 at 18:29

answered May 28, 2014 at 18:22

Karibasappa G C

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