FlattenArray.java

package test;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class FlattenArray {

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

        for (Integer i : flattenInputArray(testArray)) {
            System.out.print(i);
        }

    }

    public static Integer[] flattenInputArray(Object[] inputArray) throws IllegalArgumentException {

        if (inputArray == null)
            return null;

        List<Integer> list = new ArrayList<Integer>();

        for (Object element : inputArray) {
            if (element instanceof Integer) {
                list.add((Integer) element);
            }
            else if (element instanceof Object[]) {
                list.addAll(Arrays.asList(flattenInputArray((Object[]) element)));
            }
            else {
                throw new IllegalArgumentException("InputArray is not valid");
            }
        }
        return list.toArray(new Integer[list.size()]);
    }

}