How do I reverse my array to print out the array in reverse?

Question

public class BubbleSort {
    public static void main(String []args) {
        int[] values = {45, 67, 12, 34, 25, 39};
        int pass, comparison, temp;
        String results = "";

        for (pass = 1; pass <= values.length - 1; pass++) {
            for (comparison = 1; comparison <= values.length - pass; comparison++) {
                if (values[comparison - 1] > values[comparison]) {
                    temp = values[comparison - 1];
                    values[comparison - 1] = values[comparison];
                    values[comparison] = temp;
                }
            }
        }

        for (int i = 0; i < values.length; i++){
             results += values[i] + "\n";
        }
        System.out.print(results);
    }
}

That's my code. It prints out: 12 25 34 39 45 67

How do I reverse it so it prints out:

67 45 39 34 25 12

Also, how do I just print the array out normally like:

45 67 12 34 25 39

I'm stuck on how to print them out.

This explains how to reverse an array of type int in java: http://stackoverflow.com/questions/2137755/how-do-i-reverse-an-int-array-in-java — L.Butz, Nov 04 '14 at 15:39

score 0 · Answer 1 · answered Nov 04 '14 at 15:41

You have to revert it on your own. there is not method out of the box that does this for you.

for(int i = 0; i < values.length / 2; i++)
{
    int temp = values[i];
    values[i] = values[values.length - i - 1];
    values[values.length - i - 1] = temp;
}

If you want to print the originial values of the array you must copy it, before you modify it.

score 0 · Answer 2 · answered Nov 04 '14 at 15:41

0

for reverse:

for (int i = values.length; i >= 0; i--) results += values[i] + "\n";

for original you need to copy the origina array first before processing.

answered Nov 04 '14 at 15:41

myxlptlk

139
3

score 0 · Answer 3 · answered Nov 04 '14 at 15:41

You can do it several ways but reversing the array is not necessary to print it reversed...

results = "";
for (int i=0; i<values.length; i++) results = results+" "+values[i];
System.out.println("Non reversed :" + results);
results = "";
for (int i=0; i<values.length; i++) results = values[i]+" "+results;
System.out.println("Reversed :" + results);

Now if you really want to reverse your array you just have to exchange values both by both, first and last, second and before-last, etc. up to the middle :

for (int i=0 i<values.length/2; i++) {
  int tmp = values[i];
  values[i] = values[values.length-1-i];
  values[values.length-1-i] = tmp;
}

score 0 · Answer 4 · answered Nov 04 '14 at 15:42

This will do:

public class BubbleSort
{
    public static void main(String []args)
    {
        String results = "";
        int[] values = {45, 67, 12, 34, 25, 39};
        for (int i = 0; i < values.length; i++) results += values[i] + "\n";
        System.out.print(results);
        int pass, comparison, temp;
        results = "";
        for (pass = 1; pass <= values.length - 1; pass++)
        {
            for (comparison = 1; comparison <= values.length - pass; comparison++)
            {
                if (values[comparison - 1] > values[comparison])
                {
                    temp = values[comparison - 1];
                    values[comparison - 1] = values[comparison];
                    values[comparison] = temp;
                }
            }
        }
        for (int i = 0; i < values.length; i++) results += values[i] + "\n";
        System.out.print(results);
        results = "";
        for (int i = values.length; i >= 0; i--) results += values[i] + "\n";
        System.out.print(results);
    }
}

score 0 · Answer 5 · edited May 23 '17 at 10:33

0

There is a method in the Collections interface which reverses a List: Collections.reverse()

List<Integer> list = new ArrayList<Integer>(values); //Arrays.asList(45, 67, 12, 34, 25, 39);
Collections.reverse(list);
System.out.println(list);

For the print part remember that you have an array and arrays are tricky to print. The list instead can be printed via println with no problems.

edited May 23 '17 at 10:33

Community

1
1

answered Nov 04 '14 at 16:28

Narmer

1,414
7
16

How do I reverse my array to print out the array in reverse?

5 Answers5