Reverse array with for loop in Java

Question

I was wondering if you can help me around this code. It should reverse content of array but I get this. Does anyone know how to fix this?

import java.util.Arrays;

public class Arrays7 {

    public static void main(String[] args) {
        // Write a Java program to reverse an array of integer values.
        
        int arr[] = { 1, 2, 3, 4, 5};
        int petlja[] = { 0, 0, 0, 0, 0 };       
        
         /* arr[0] = petlja[4];
        arr[1] = petlja[3];
        arr[2] = petlja[2];
        arr[3] = petlja[1];
        arr[4] = petlja[0];
        */
        
        for ( int i=4; i>0; i--) {
            for ( int j=0; j<4; j++) {
                petlja[j] = arr[i];
            }
        }
        
        System.out.println(Arrays.toString(petlja));

I think you're just guessing, which doesn't help you learn. Write down the steps to do this by hand. Then try to duplicate those steps on the computer. Hint: you only need one loop, not two nested loops. — markspace
– markspace, Commented Sep 25, 2020 at 19:39
If you still aren't able to figure out, Swap the first and the last element of the array and write down how the computer will execute it and according set the condition. — Swapnil Padaya
– Swapnil Padaya, Commented Sep 26, 2020 at 1:09

Mureinik · Accepted Answer · 2020-09-25 19:40:06Z

1

You don't need a nested loop - you need only one loop to go over the array and assign each element to the corresponding "reversed" array:

for (int i = arr.length - 1; i >= 0; i--) {
    petlja[petlja.length - i] = arr[i];
}

answered Sep 25, 2020 at 19:40

Mureinik

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Spectric · Accepted Answer · 2020-09-25 19:46:22Z

0

You can do it like so:

    for(int i = 0; i < array.length; i++) {
        petlja[i] = arr[array.length-i-1];
    }

Sample I/O

Input

1, 2, 3, 4, 5

Output

5, 4, 3, 2, 1

answered Sep 25, 2020 at 19:46

Spectric

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