java - 局部变量可能尚未初始化构造函数/方法

Question

代码还远未完成，但我基本上一直停留在这个问题上，直到我可以进一步前进。继续获取本地变量可能尚未在他们的电话上初始化。如果我将构造函数移动到 try catch，我会在 try catch 上收到错误，如果我保持原样，我会在 yourPhone.getAreaCode(phoneNumber) 处收到错误)；有什么帮助吗？

import java.util.Scanner;

public class CustomerTelephone {

    public static void main(String[] args) {
        CustomerTelephone theirPhone;
        String phoneNumber = "407 407 4074";

        try {
            theirPhone = new CustomerTelephone(phoneNumber);
        } catch (InvalidTelephoneException ite) {
            System.out.println("Invalid telephone number format.");
        }

        theirPhone.getAreaCode(phoneNumber);

    }

    public CustomerTelephone(String telephone) throws InvalidTelephoneException {
        if (telephone.length() != 12) {
            throw new InvalidTelephoneException(
                "The phone number was entered incorrectly.");
        }
    }

    public String getAreaCode(String phoneNumber) {
        String goBack;
        String[] teleArray = phoneNumber.split("(?!^)");
        goBack = teleArray[0 - 2];

        return goBack;
    }

    public String getExchange(String phoneNumber) {
        String goBack = null;

        return goBack;
    }

    public String getLocalNumber(String phoneNumber) {
        String goBack = null;

        return goBack;
    }

}

Answer 1

简单修复:将引用初始化为 null:

CustomerTelephone theirPhone = null;

更好的修复:初始化变量并将对该变量的引用移至 try block 中。因此，如果在 try block 中引发异常，则可以避免后续的 NullPointer 异常。

CustomerTelephone theirPhone = null;
 ...
try {
    theirPhone = new CustomerTelephone(phoneNumber);
    theirPhone.getAreaCode(phoneNumber);
} catch {
...
}