Array demo, static and dynamically sized.

ArrayDemo.sol

pragma solidity 0.5.12;

contract ArrayDemo {
    uint64[] dynamicArray = [1, 2, 3];
    uint64[3] staticArray = [1,2,3];
    
    function getDynamicArray(uint64 index) public view returns(uint64){
        return dynamicArray[index];
    }
    
    function setDynamicArray(uint64 newNumber, uint index) public{
        dynamicArray[index] = newNumber;
    }
    
    function pushDynamicArray(uint64 newNumber) public{
        dynamicArray.push(newNumber);
    }
    
    function getStaticArray(uint64 index) public view returns(uint64){
        return staticArray[index];
    }
    
    function setStaticArray(uint64 newNumber, uint64 index) public{
        staticArray[index] = newNumber;
    }
}