My even numbers method doesn't return the even number

Question

This code print the array (1, 7, 8, 22, 37, 55, 80) the way it is without calculating its evens.

The output that I want (8, 22, 80).

The output that I get (1, 7, 8, 22, 37, 55, 80).

///The getEvens() method
public static int[] getEvens(int a[]) {

    int myEvens = 0;

    for (int i = 0; i < a.length; i++) {
      if (a[i] % 2 == 0) {
         myEvens++;
      }    
    }

    Arrays.sort(a);

    return a;
}

\\\\The main method
public static void main(String args[]) {

    int [] getEvens;
    int [] myArray = {1,8,80,22,55,37,7};
    int [] evenResult = getEvens(myArray);

    System.out.print("\nThe even numbers in the array(" +    Arrays.toString(myArray)+ ") are:{ " + Arrays.toString(evenResult)+ "}.");

}

Your code identifies the evens but doesn't do anything with them. Maybe consider creating a new array, adding the evens to that, and then returning it? — jeff carey, Oct 10 '16 at 17:34

score 2 · Answer 1 · edited May 23 '17 at 11:48

2

One of the issues is that you are not returning anything from the getEvens() method, so your second toString will not give you what you need. Also you increment myEvens, but this value is functioning as a counter. You need to save the even value that is in the array.

You can do this with ArrayList easily:

//import ArrayList
import java.util.ArrayList;
//before method
List<Integer> evens = new ArrayList<Integer>();
//in the for-loop
evens.add(a[i]);

See more on ArrayLists here.

If you want to continue working with arrays, you could create a new array of length myEvens, run through your original loop again, and add each even value to your new array. However, to do this, you would need a way to keep track of which index you are on in your new array.

Sorting algorithms are available online. array.sort() works for array values. ArrayList implementation of sort is given here.

edited May 23 '17 at 11:48

Community

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answered Oct 10 '16 at 17:43

Sondering Narcissist

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error i get: ** symbol : class List location: class Method2 List evens = new ArrayList(); ^ 1 error ** – Bret Dun Oct 10 '16 at 17:57
Probably worth mentioning that the static method [`Collections.sort`](https://docs.oracle.com/javase/7/docs/api/java/util/Collections.html#sort(java.util.List)) is the equivalent method when working with lists. – nbrooks Oct 10 '16 at 17:57
if u don't mind, please put it in my code and show it here. I'm trying so hard but still getting errors – Bret Dun Oct 10 '16 at 18:51
import java.util.*; ArrayList evens = new ArrayList(); public static List getEvens(int[]a){ for(int i:a){ if(i%2) == 0{ evens.add(i); } Collections.sort(evens); } return evens; } – Sondering Narcissist Oct 11 '16 at 22:24

score 0 · Answer 2 · answered Oct 10 '16 at 17:44

0

Right now, all you're doing is counting the number of evens in your array, which is fine if that's all you want to do. If you actually want them to be extracted into their own array, that's trickier since arrays aren't dynamic.

You have two options and I would prefer the latter:

Create a List<Integer> and store the values there, then extract them into an array (if you so desire):

// Declare this list outside of the loop
List<Integer> evens = new ArrayList<>();
if(a[i] % 2 == 0) {
    evens.add(a[i]);
}
return evens.toArray(new int[0]);

Use Arrays.stream to build a stream and filter out an array with only the even values:

// Just return this explicitly
return Arrays.stream(a).filter(i -> i % 2 == 0)
                       .toArray();

answered Oct 10 '16 at 17:44

Makoto

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Depends on your errors. I listed my suggestions here as a guideline. The latter suggestion will only work with Java 8, so be sure you have that installed. – Makoto Oct 10 '16 at 17:55
error i get: **bold** symbol : class List location: class Method2 List evens = new ArrayList(); ^ 1 error – Bret Dun Oct 10 '16 at 17:56
You should import `java.util.List` and `java.util.ArrayList` into your class. – Makoto Oct 10 '16 at 17:59
if u don't mind, please put it in my code and show it here. I'm trying so hard but still getting errors(The first option) – Bret Dun Oct 10 '16 at 18:52
I do mind; I've only elected to give you a hint here. It is entirely up to you to understand how to incorporate it in your code. – Makoto Oct 10 '16 at 19:01

score 0 · Answer 3 · answered Oct 10 '16 at 18:00

0

Since nobody mentioned it, here is a concise version for Java 8:

public static int[] getEvens(int a[]) {
    Arrays.stream(a).filter(i -> i % 2 == 0).toArray();
}

answered Oct 10 '16 at 18:00

khachik

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This looks so clean..Let me try it out..unfortunately i'm not able to install Java 8..only 6 – Bret Dun Oct 10 '16 at 18:01
I think you're missing a `return` – nbrooks Oct 10 '16 at 18:19
[Wait a minute...I'm pretty sure I mention this...](http://stackoverflow.com/a/39963890/1079354) ;) – Makoto Oct 10 '16 at 19:04

score -2 · Answer 4 · answered Oct 10 '16 at 17:38

-2

You're actually just sorting and returning the same array that was passed into your method. In your if-statement where you're counting "myEvens" you could add a[i] to a new array and then return that one instead of a (which is the input-parameter).

answered Oct 10 '16 at 17:38

TenaciousG

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what size would you assign to such an array? – austin wernli Oct 10 '16 at 17:42
Use an ArrayList or similar like suggested in another post, not an array. I'm sure you'll work it out. – TenaciousG Oct 10 '16 at 17:50

Geeky · Answer 5 · 2016-10-10T17:49:43.580

-2

Your code is trying to count the number of evens you have in the array. As @jeff carey said you can create new array and evens to them. Following is the code snippet for you

   public static List<int> getEvens(int []  a) {

int myEvens = 0;
        int [] evenArray=new int[3];
        List<int> evenList=new List<int>();
        int length=a.Length;
        int index=0;

for (int i = 0; i <length; i++) {

  if (a[i] % 2 == 0) {

     myEvens++;
     evenList.Add(a[i]);
  }    

}

 Array.Sort(a);

 return evenList;
}

Hope this helps

edited Oct 10 '16 at 17:49

answered Oct 10 '16 at 17:42

Geeky

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why would you assign a value of 3 as the array size? Would suggesting another data structure be better for this case? – austin wernli Oct 10 '16 at 17:44
You can't use generics with a primitive type. `List` is a no-go. – Makoto Oct 10 '16 at 17:54

My even numbers method doesn't return the even number

5 Answers5