How do I use parts of an old array to create a new one in java?

Question

So I need to create a new array that swaps the first and last values of my existing array. Here's what I have so far:

import java.util.Scanner;
import java.util.Arrays;
public class P9_ArrayManipulate
{    public static void main (String[] args)
 {   Scanner in = new Scanner(System.in);
    System.out.println("Please enter seven numbers for an Array.");
    int []array = new int[7];
    int total = 0;
    for (int i = 0; i < 7;i++){
            array[i] = in.nextInt();
    }
    System.out.println("Your reversed array is "+reverseArray(array));
    System.out.println("Your swapped array is "+swapArray(array));
    System.out.println("Your array without even numbers is "+evenArray(array));
    System.out.println("The program has finished calling array methods.");
}
 public static int []reverseArray(int []array)
{   int[] reversed = new int[array.length];
    int i;
    for(i=0; i < array.length; i++)
    {
        reversed[i] = array[(array.length - i -1)];
    }
    return reversed;
}
public static int []swapArray (int []array)
{   
  array[0] += array[array.length-1];
  array[array.length-1] = array[0] - array[array.length-1];
  array[0] -= array[array.length-1];
  return array;
}
public static int []evenArray(int []array)
{   for (int i = 0; i < array.length;i++){
    if (array[i]%2 !=0)
    {array[i] = 0;}
    i++;}
    return array; 
}

}

Everything compiles correctly (as far as I can tell), but I'm getting a weird run time error. After seven inputs, I get this as my output: Your reversed array is [I@b4d079 Your swapped array is [I@3644d1 Your array without even numbers is [I@3644d1 The program has finished calling array methods.

What is the error? Is it the weird formatting of the messages? That's because arrays are not automatically converted to strings. You might want to try System.out.println("Your reversed array is "+Arrays.toString(reverseArray(array))); — Ken Geis, Nov 04 '15 at 05:24

score 0 · Answer 1 · answered Nov 04 '15 at 04:20

0

You have to import Arrays from java.util.Arrays

answered Nov 04 '15 at 04:20

Ramanlfc

8,283
1
18
24

Got it, now I'm having issues combining the parts of the old array into the new one. It doesn't like the +. – Colleen Nov 04 '15 at 04:22

Sekula1991 · Answer 2 · 2015-11-04T04:44:09.640

Try something like this:

*Edit: If its a must to create new array, just create int newarray[] = method(); instead of array[]=method();

  import java.util.Scanner;
  public class Array 
 {
public static void main (String[] args)
{   Scanner in = new Scanner(System.in);

System.out.println("Please enter seven numbers for an Array.");
int []array = new int[7];
for (int i = 0; i < 7;i++){
    array[i] = in.nextInt();
}

array = reverseArray(array);
System.out.println("Your reversed array is :");
for (int i = 0; i < array.length; i++) {
    System.out.print(array[i]+" ");
}
System.out.println();

array = swapArray(array);
System.out.println("Your swapped array is :");
for (int i = 0; i < array.length; i++) {
    System.out.print(array[i]+" ");
}
//          System.out.println("Your array without even numbers is "+evenArray(array));
System.out.println();
System.out.println("The program has finished calling array methods.");
}
public static int[] reverseArray(int []array)
{   int left = 0;
int right = array.length-1;
while(left<right){
    int reverse = array[left];
    array[left]=array[right];
    array[right] = reverse;
    left++;
    right--;
}
return array;
}
public static int []swapArray (int []array)
{   
    int help = 0;
    help = array[0];
    array[0] = array[6];
    array[6] = help;

    return array;
  }
 }

score 0 · Answer 3 · edited May 23 '17 at 11:51

0

You may use the following answer to merge the arrays in swapArray() method

How can I concatenate two arrays in Java?

edited May 23 '17 at 11:51

Community

1
1

answered Nov 04 '15 at 04:39

Hasan

21
3

score 0 · Accepted Answer · answered Nov 04 '15 at 04:59

0

It would be much easier to just swap the first and last values of the array passed in to the swapArray() function and return that instead of creating a new array.

Something like the following will work (and it doesn't create a new variable to facilitate swapping):

public static int[] swapArray(int[] array) {
    array[0] += array[array.length-1];
    array[array.length-1] = array[0] - array[array.length-1];
    array[0] -= array[array.length-1];
    return array;
}

answered Nov 04 '15 at 04:59

Shadow

3,926
5
20
41

Thank you, this helped me figure it out. – Colleen Nov 04 '15 at 05:08
@Colleen No worries, if it solved your problem please accept it as the answer by clicking the tick mark – Shadow Nov 04 '15 at 05:11
So everything compiles now, but I'm getting a strange output. I updated the question with my output. – Colleen Nov 04 '15 at 05:21

How do I use parts of an old array to create a new one in java?

4 Answers4