Why am I getting an "invalid method declaration; return type required" error on **check(values);** ?

```
public class Swap
{
    int[] values = {5, 6, 7, 8, 9};
    check(values);

    public void swapAdjacentElemnts(int[] values)
    {
        for(int i=0; i<values.length - 1; i+=2)
        {
            int tempInt = values[i];
            values[i] = values[i+1];
            values[i+1]=tempInt;
        }
    }

    public int[] check(int[] values)
    {
        swapAdjacentElements(values);
        return values;
    }
}

```