Question

Rather trivial piece of Java code here.. But getting an OutOfBoundsException and I’m not quite sure why? Any help would be great!

Before anyone asks if this is homework, no it isn’t it’s for exam prep.

import java.util.Scanner;
public class exampractice {

    public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);

        int[] a = {1,2,3};
        int min = a[0];
        int max = a[0];

        for (int i = 0; i <= a.length; i++){
            if(a[i] < min)
                min = a[i];
            else
                if(a[i] > max)
                    max = a[i];
        }

        System.out.println("Min is"+min+ "\nMax is: " + max);
    }
}

Answer 1

It should be < not <=. Zero based indices on an array vary from 0 to length - 1.

Update

Someone in grad school taught me to build up a collection of mental patterns like this and use them; you’ll avoid bugs. This one is that any array in a C-like language is always searched as

for(index = 0; index < array.length ; index++)

Having trained myself over the years with this, I saw this bug at, literally, first glance, which is how I got in at the head of the line.

Here’s are some more examples, for C:

 char aString[MAXLENTH];  // declare a string array
 char * aString ;
 aString = (char *) malloc(MAXLENGTH]; // or malloc it

 // constructing a string with catenation
 aString[0] = '\0';       // now either way this is guaranteed an empty string

But of course I should have used another pattern:

 if((aString = (char *) malloc(MAXLENGTH) == NULL){
     // report out of memory
     exit(BAD);
 }

Think about what other patterns might be good.