public class Numbers {
	public static final int DEFAULT_CAPACITY = 10;
	private int[] numbers;
	private int currentPos = 0;

	public Numbers(){
		this(DEFAULT_CAPACITY);
	}
	public Numbers(int capacity){
		numbers = new int[capacity];
	}

	//if is full we leave otherwise insert number
	public void add(int num){
		if(isFull()) return;
		insertNumInPos(num, currentPos);
		incrementPos();
	}

	public String toString(){
		StringBuilder s = new StringBuilder("[");
		for(int i =0; i < size(); ++i){
			s.append(getNumber(i));
			if(i < size() - 1)
				s.append(",");
		}
		s.append("]");
		return s.toString();
	}

	public int getNumber(int pos){
		return numbers[pos];
	}

	public int size(){
		return currentPos;
	}

	public int capacity(){
		return numbers.length;
	}

	private void insertNumInPos(int num, int pos){
		numbers[pos] = num;
	}

	private void incrementPos(){
		currentPos++;
	}

	public boolean isFull(){
		return currentPos == numbers.length;
	}

	public boolean isEmpty(){
		return currentPos == 0;
	}
}


//testclass with main method
import java.util.Random;
public class ArrayMergeDemo{
	public static void main(String[] args){
		//nums1 intialized with twice the capacity of nums2
		Numbers nums1 = new Numbers(20),nums2 = new Numbers();
		//lets fill them with random numbers just from 0 to nums2 capacity
		Random randomNumsGenerator = new Random();
		for(int i = 0; i < nums2.capacity(); ++i){
			nums1.add(randomNumsGenerator.nextInt(10));
			nums2.add(randomNumsGenerator.nextInt(10));
		}

		System.out.println("contents of nums1 : " + nums1);
		System.out.println("contents of nums2 : " + nums2);
		if(arraysCanBeMerged(nums1,nums2)){
			merge(nums1,nums2);
			System.out.println("contents of nums1 after merge : " + nums1);
		}
	}

	public static boolean arraysCanBeMerged(Numbers to, Numbers from){
		return to.capacity() >= (to.size() + from.size());
	}

	public static Numbers merge(Numbers to, Numbers from){
		for(int num = 0; num < from.size(); ++num)
			to.add(from.getNumber(num));
		return to;
	}
}