Check.sol

pragma solidity ^0.5.0;

contract Token {

    mapping (address => uint) tokenBalance;
    mapping (address => uint) etherBalance;
    uint currentRate;

    constructor() public {
        currentRate = 2;
    }
    
    function getTokenCountFor(address x) public view returns(uint) {
        return tokenBalance[x];
    }
    function getEtherCountFor(address x) public view returns(uint) {
        return etherBalance[x];
    }
    
    function getTokenCount() public view returns(uint) {
        return tokenBalance[msg.sender];
    }

    function depositEther() public payable {
        if (msg.value > 0) { etherBalance[msg.sender] += msg.value; }
    }

    function exchangeTokens(uint amount) public {
        if (tokenBalance[msg.sender] >= amount) {
            uint etherAmount = amount * currentRate;
            etherBalance[msg.sender] += etherAmount;
            tokenBalance[msg.sender] -= amount;
        }
    }

    function exchangeEther(uint amount) public payable {
        etherBalance[msg.sender] += msg.value;
        if (etherBalance[msg.sender] >= amount) {
            uint tokenAmount = amount / currentRate;
            etherBalance[msg.sender] -= amount;
            tokenBalance[msg.sender] += tokenAmount;
        }
    }
    function transferToken(address to, uint amount) public {
        if (tokenBalance[msg.sender] >= amount) {
            tokenBalance[to] += amount;
            tokenBalance[msg.sender] -= amount;
        }
    }
    
    function exchangeAndWithdrawToken(uint amount) public {
        if (tokenBalance[msg.sender] >= amount) {
            uint etherAmount = tokenBalance[msg.sender] * currentRate;
            tokenBalance[msg.sender] -= amount;
            msg.sender.transfer(etherAmount);
        }
    }

    function withdrawAll() public {
        uint etherAmount = etherBalance[msg.sender];
        uint tokenAmount = tokenBalance[msg.sender];
        if (etherAmount > 0 && tokenAmount > 0) {
            uint e = etherAmount + (tokenAmount * currentRate);
        etherBalance[msg.sender] = 0;
            msg.sender.call.value(e)("");
            tokenBalance[msg.sender] = 0;
        }
    }
}