```//SPDX-License-Identifier: MIT
pragma solidity >=0.8.0;

//0x534725eE6e6f99Cd74882F44DA70f2db320470b5
contract hello {
    string public Msg;

    uint256 public number;

    // 原mapping
    mapping(address => uint256) public blance;
    //通过下标记录原mapping 的key
    mapping(uint256 => address) record;
   // maping  的长度
    uint256 len = 0;

    uint256 total;

    event transferEvent(
        address indexed from,
        address indexed to,
        uint256 amount
    );

    constructor() payable {
        Msg = "hello world";
    }

    //mapping 插入
    function add(address acount, uint256 amunt) public {
        len++;
        blance[acount] = amunt;
        // 计数 mapping
        record[len - 1] = acount;
        
    }

   //maping  遍历
    function getTotal() public returns (uint) {
        for (uint256 i = 0; i < len; i++) {
            total = total + blance[record[i]];
        }
        return  total;
    }

    function store(uint256 _number) external {
        number = _number;
    }

    function getNumber() public view returns (uint256) {
        return number;
    }

    // 获取合约当前余额 0xf188A42123C088C1330BFEA35a34298623D26386
    function getContractBalance() external view returns (uint256) {
        return address(this).balance;
    }

    function transfer(address to, uint256 amount) public {
        // (bool success, ) = to.call{value: amount}(new bytes(0));
        // require(success, "safeTransferETH: ETH transfer failed");

        payable(to).transfer(amount);

        emit transferEvent(msg.sender, to, amount);
    }

    function getBalance(address _address) external view returns (uint256) {
        return address(_address).balance;
    }

    receive() external payable {}
}

```