我正在努力弄清楚我的代码有什么问题。我要求用户插入以下格式:
LeftOperand operator RightOperand
在哪里:
- LeftOperand - 可以是任何整数或浮点数
- 运算符 - 可以是 +、-、* 或 /
- RightOperand - 可以是任何整数或浮点数
我搜索并发现了一些正则表达式,但它们似乎都不适用于我,因为除了以下内容之外的任何内容:3 +/-/*// 5
返回错误。应该是有效的:
- 1 + 3
- 1 / 4
- 1.3 - 4
- 4 - 5.3
- 123 * 3434
- 12.34 * 485
但实际上只有那些是有效的,而其余的则返回错误:
- 1 + 3 - 正确
- 1 / 4 - 正确
- 1.3 - 4 - 错误
- 4 - 5.3 - 错误
- 123 * 3434 - 错误
- 12.34 * 485 - 错误
我目前在我的代码中使用以下正则表达式:
"[((\\d+\\.?\\d*)|(\\.\\d+))] [+,\\-,*,/] [((\\d+\\.?\\d*)|(\\.\\d+))]"
尝试了各种正则表达式,但似乎都不起作用,我只是不知道我做错了什么:
[[+-]?([0-9]*[.])?[0-9]] [+,\-,*,/] [[+-]?([0-9]*[.])?[0-9]]
这是我的客户代码:
private static final int SERVER_PORT = 8080;
private static final String SERVER_IP = "localhost";
private static final Scanner sc = new Scanner(System.in);
private static final String regex = "[((\\d+\\.?\\d*)|(\\.\\d+))] [+,\\-,*,/] [((\\d+\\.?\\d*)|(\\.\\d+))]";
public static void main(String[] args) throws IOException {
// Step 1: Open the socket connection
Socket serverSocket = new Socket(SERVER_IP, SERVER_PORT);
// Step 2: Communication-get the input and output stream
DataInputStream dis = new DataInputStream(serverSocket.getInputStream());
DataOutputStream dos = new DataOutputStream(serverSocket.getOutputStream());
//Run until Client decide to disconnect using the exit phrase
while (true) {
// Step 3: Enter the equation in the form -
// "operand1 operation operand2"
System.out.print("Enter the equation in the form: ");
System.out.println("'operand operator operand'");
String input = sc.nextLine();
// Step 4: Checking the condition to stop the client
if (input.equals("exit"))
break;
//Step 4: Check the validity of the input and
// return error message when needed
if (input.matches(regex)) {
System.out.println("Expression is correct: " + input);
} else {
System.out.println("Expression is incorrect, please try again: ");
continue;
}
// Step 5: send the equation to server
dos.writeUTF(input);
// Step 6: wait till request is processed and sent back to client
String ans = dis.readUTF();
// Step 7: print the response to the console
System.out.println("Answer=" + Double.parseDouble(ans));
}
}