How do I reverse the integers in one array using another array?

Question

I have gotten 10 values from the user, and I am suppose to put that into an array and call it into a method, and then call another method which contains an array that reverses the integers of the first array without using global variables. For example, the user gives me values 1,2,3, etc.. and I store that in the first array, then in the second array I output 3,2,1.

I have part of the code that gets the integers from the user, but I don't know how to reverse the array without using global variables. The code doesn't run when it gets to the second method at values[i];

Here is what I have so far:

public static void main(String[] args) {

    getInput();
    reverseInput();
    System.exit(0);
}  

public static void getInput() {

    Scanner keyboard = new Scanner(System.in);

    int[] values;
    values = new int[10];

    //Ask the user to enter 10 integers
    System.out.println("Please enter ten numbers.");
    for (int i = 0; i<values.length; i++) {//for loop to display the values entered
        values[i] = keyboard.nextInt();
        System.out.println("Value" + (i +1) + " is " + values[i]);
    }
}

public static void reverseInput() { 

    System.out.println("Now we are going to reverse the numbers.");
    Scanner keyboard = new Scanner(System.in);

    int [] values;
    values = new int[10];

    for (int i = (values.length -1); i>= 0; i--) {//for loop to display integers in reversed order
        values[i];
        System.out.println(values[i]);
    }
}

Michaeldcooney · Accepted Answer · 2011-12-07 01:48:04Z

3

First, if you are not going to be using global variables, then you will need to pass the array from the get input method to the reverseInput method. Something like this:

int[] values = getInput();
reverseInput(values);

Then to output the array in your reverseInput method, it would have to look like this:

    public static void reverseInput(int[] values) {
        for(int i = (values.length - 1); i >= 0; i--){
            System.out.println(values[i]);
        }
    }

answered Dec 7, 2011 at 1:48

Michaeldcooney

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4 Comments

rahme24 Over a year ago

Okay, that makes sense, but my question now is where exactly do I do that? It won't compile when I did it in the reverseInput method, so would I maybe do it in the main method?

Michaeldcooney Over a year ago

You need to remove the line where you have "values[i];"

rahme24 Over a year ago

I removed that. Is that where I pass the array?

Michaeldcooney Over a year ago

You pass the array in the main method from the getInput to the reverseInput like the first two lines of code above show.

Elias Dorneles · Accepted Answer · 2011-12-07 01:56:07Z

2

You can use the ArrayUtils.reverse from Commons Lang:

ArrayUtils.reverse(values);

edited Dec 7, 2011 at 1:56

answered Dec 7, 2011 at 1:46

Elias Dorneles

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3 Comments

QuantumMechanic Over a year ago

I think the idea is that he's supposed to write his own reverse function.

rahme24 Over a year ago

Yes I am supposed to write the array that reverses the input of the first array.

Elias Dorneles Over a year ago

ahh! sorry! well, if you're doing it to learn, I suggest you do it step-by-step just in a piece of paper first, and THEN you try to code it.

QuantumMechanic · Accepted Answer · 2011-12-07 01:49:07Z

1

Ok, you understand how to display the elements in reference order. As you wrote:

for (int i = (values.length - 1); i >= 0; i--) {
    System.out.println(values[i]);
}

So given that, how would you put the elements of values (say it has 5 elements) in another array (call it reversedValues) such that values[4] was put into reversedValues[0] and so on up to values[0] being put into reversedValues[4]?

answered Dec 7, 2011 at 1:49

QuantumMechanic

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Comments

score 1 · Accepted Answer · 2011-12-07 02:22:59Z

1

use the "getInput" as basis to get the 10 numbers, then after the "for" loop, just do another for loop in reverse

  public static void reverseInput()
  {

    Scanner keyboard = new Scanner(System.in);

    int[] values;
    values = new int[10];

    //Ask the user to enter 10 integers
    System.out.println("Please enter ten numbers, we are going to reverse the numbers");
    for (int i = 0; i<values.length; i++) //for loop to display the values entered
    {
      values[i] = keyboard.nextInt();
    };
    int[] revValues;
    revValues = new int[10];
    for (int i = (values.length -1); i>= 0; i--) //for loop to display integers in reversed order
    {
      revValues[ revValues.length -1 -i ] = values[ i ];
      System.out.println( revValues[ i ] );
    }
}

edited Dec 7, 2011 at 2:22

answered Dec 7, 2011 at 1:46

user497849

2 Comments

rahme24 Over a year ago

But I have to do two separate arrays, the second one using the values of the first.

user497849 Over a year ago

OK, I've updated the answer to fill "revValues" array with values of "values" array in reverse.

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