Truffle pet shop tutorial contract

Adoption.sol

pragma solidity ^0.4.4;

contract Adoption {
    
    address[16] public adopters;


    // Adopting a pet
    function adopt(uint petId) public returns (uint) {
      require(petId >= 0 && petId <= 15);
    
      adopters[petId] = msg.sender;
    
      return petId;
    }
    
    // Retrieving the adopters
    function getAdopters() public constant returns (address[16]) {
      return adopters;
    }
        
}