erc20.sol

pragma solidity ^0.4.20;

import './erc20interface.sol';

contract ERC20 is ERC20Interface {

    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) internal allowed;

    constructor() public {
        totalSupply = 1000;
        name = "JueJin Token";
        symbol = "JJT";
        decimals = 0;
        balanceOf[msg.sender] = totalSupply;
    }

  function balanceOf(address _owner) view returns (uint256 balance) {
      return balanceOf[_owner];
  }

  function transfer(address _to, uint _value) public returns (bool success) {
      require(_to != address(0));
      require(_value <= balanceOf[msg.sender]);
      require(balanceOf[_to] + _value >= balanceOf[_to]);

      balanceOf[msg.sender] -= _value;
      balanceOf[_to] += _value;
      emit Transfer(msg.sender, _to, _value);
      return true;
    }

    function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
      require(_to != address(0));
      require(_value <= balanceOf[_from]);
      require(_value <= allowed[_from][msg.sender]);
      require(balanceOf[_to] + _value >= balanceOf[_to]);

      balanceOf[_from] -= _value;
      balanceOf[_to] += _value;

      allowed[_from][msg.sender] -= _value;
      emit Transfer(_from, _to, _value);
      return true;
    }

  function approve(address _spender, uint256 _value) returns (bool success) {
      allowed[msg.sender][_spender] = _value;
      emit Approval(msg.sender, _spender, _value);
      return true;
  }

  function allowance(address _owner, address _spender) view returns (uint256 remaining) {
      return allowed[_owner][_spender];
  }

}