I want to reverse an array but dont know why this error comes?-CodePudding

i dont kow ehy my programs dont run. i am trying to reverse my array through user defined function. i can give an input but cannot find out the answer.

import java.util.*;
public class reverseanarray{
public static int reversea(int array[]){
    int swap;
    int j=array.length;
    for(int i=0;i<array.length/2;i  ){
        swap=array[i];
        array[i]=array[j];
        array[j]=swap;
        j--;
    }
    return j;
}      
public static void main(String args[]){
   Scanner sc = new Scanner(System.in);
   //System.out.println();
   //int a = sc.nextInt();
   System.out.println("please input the length");
   int y=sc.nextInt();//INPUT OF LENGTH OF ARRAY
   int arr[]=new int[y];
       //INPUT ARRAY
       for(int r=0;r<arr.length;r  ){
           System.out.println("please input the " r " index value");
           arr[r]=sc.nextInt();
       }
       System.out.println(reversea(arr));
       for(int i=0;i<y;i  ){
        System.out.println(arr[i]);
       }
      
    }

}

CodePudding user response：

The code is giving you an ArrayIndexOutOfBoundsException, as you are trying to address an array index which is beyond array limits. The reason for this is, that arrays are 0-indexed, so an array of length 10 has indexes 0-9. Your code does not take this into account when defining field j.

The only change you need to make is change that line:

int j = array.length;

into this one:

int j = array.length - 1;

You could also do some more refactoring and rewrite method as:

public static int[] reversea(int array[]) {
    int swap;
    for (int i = 0, j = array.length-1; i < j; i  , j--) {
        swap = array[i];
        array[i] = array[j];
        array[j] = swap;
    }
    return array;
}

Instead of returning useless value of j after reversing, the refactored method returns the array in reversed order.

PS: Please use CamelCase for your class names.