How to print a method returning an array?

Question

I made a method converting a 2D array into a 1D array but I'm having troubling printing it. There's a problem with making a new array in the main method or calling the method. anyone can help??

public class flatten {

public static int[] flatten1(int[][] a){
    int c=0;
    for(int i=0;i<a.length;i++){
        for(int j=0;j<a[i].length;j++){
            c++;
        }   
    }

    int[] x = new int[c];
    int k=0;

    for(int i=0;i<a.length;i++){
        for(int j=0;j<a[i].length;j++){
            x[k++]=a[i][j];
        }
}
    return x;
}
public static void main(String[]args){
    flatten1 f = new flatten1({{2,5,3,7,4,8},{3,4,1,2}});
    for(int i=0; i<f.length;i++){

        System.out.print(f[i]+" ");
    }

}

}

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

Firstly you cannot do this:

   flatten1 f = new flatten1({{2,5,3,7,4,8},{3,4,1,2}});

flatten1 is not a class it is a method, you cannot instantiate flatten1 and input a 2D int array. For the above to legal, you would need to create a class called flatten1 and create a constructor which takes a 2D int array as a parameter and I believe that is not what you want to do.

Your flatten method works perfectly fine, change your main method to the following:

public static void main(String[] args){
   int[][] arrayToBeFlattened = {{2,5,3,7,4,8},{3,4,1,2}};
   int[] oneD = flatten1(arrayToBeFlattened);

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

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Sep 3, 2015 at 23:20

RamanSB

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Comments

meritus · Accepted Answer · 2015-09-03 23:24:11Z

Try this:

public class flatten {

    public static int[] flatten1(int[][] a) {
        int c = 0;
        for (int i = 0; i < a.length; i++) {
            for (int j = 0; j < a[i].length; j++) {
                c++;
            }
        }

        int[] x = new int[c];
        int k = 0;

        for (int i = 0; i < a.length; i++) {
            for (int j = 0; j < a[i].length; j++) {
                x[k++] = a[i][j];
            }
        }
        return x;
    }

    public static void main(String[] args) {
        int[][] test_arr = { { 1, 2, 3 }, { 4, 5, 6 } };

        int[] f = flatten.flatten1(test_arr);
        for (int i = 0; i < f.length; i++) {

            System.out.print(f[i] + " ");
        }

    }
}

ninesalt · Accepted Answer · 2015-09-03 23:26:19Z

0

In your main method, when you print f[i] you're not printing the first value. Since f is an array of arrays you're trying to print the ith array not the i'th element. Make sure you understand this distinction because it's important. Printing the ith array will simply give you its memory address.

To fix this, simply change your print statement to:

System.out.print(Arrays.toString(f[i])+" ");

answered Sep 3, 2015 at 23:26

ninesalt

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