为我要包含的长代码道歉。我想要做的是将某些经过验证的用户输入变量保存到对象中。我认为我的问题是由于变量范围，这就是我犯错误customerAccount may not have been initialized的原因。
如果有人能指出我正确的方向，我们将非常感激。
import java.util.*;
import java.io.*;
public class ATM {
public void run() {
// USED FOR DEBUGGING PURPOSES. SET TO TRUE TO ENABLE DEBUGGING MODE
boolean debug = false, mainCheck = false, check = false;
Scanner input = new Scanner(System.in);
Scanner fInput = null;
int idNumber = 0;
String lastName, firstName, emailAddress, phoneNumber;
double startingBalance;
Client customerAccount;
File file = new File("accountData.txt");
if(!file.exists()) {
System.out.println("File does not exist within directory. Creating file now.");
PrintWriter output = null;
try {
output = new PrintWriter(file);
}
catch(IOException e) {
System.out.println("Something went wrong during file creation.");
}
finally {
if (output != null)
output.close();
}
}
ArrayList<Client> clientArr = new ArrayList<Client>();
try {
fInput = new Scanner(new File("accountData.txt"));
}
catch(Exception e) {
System.out.println("ERROR: File Not Found.");
e.printStackTrace();
}
while(fInput.hasNext()) {
try{
int tempID = fInput.nextInt();
String tempFName = fInput.next();
String tempLName = fInput.next();
String tempPNumber = fInput.next();
String tempEmail = fInput.next();
double tempBalance = fInput.nextFloat();
Client tempClient = new Client(tempID, tempFName, tempLName, tempPNumber, tempEmail, tempBalance);
tempClient.getAccount().setID(tempID);
clientArr.add(tempClient);
if(debug == true)
System.out.println(tempID+" "+tempFName+" "+tempLName+" "+tempPNumber+" "+tempEmail+" $"+tempBalance);
}
catch(NoSuchElementException e) {
System.out.println("ERROR: Missing a required data field.");
}
}
if(debug == true)
System.out.println(clientArr.size());
int menuChoice = 0;
while(menuChoice != 5) {
System.out.println("**********************************");
System.out.println("Thank you for choosing Java World Bank!");
System.out.println("Main Menu: ");
System.out.println("[1] Login as an existing user.");
System.out.println("[2] Display client list sorted by last name.");
System.out.println("[3] Display client list sorted by account number.");
System.out.println("[4] Create a new client.");
System.out.println("[5] Exit.");
System.out.println("====================================");
do {
try {
System.out.println("Enter your choice: ");
menuChoice = input.nextInt();
mainCheck = true;
}
// Checks if user enters an unexpected input (not a digit)
catch(InputMismatchException e) {
System.out.println("Invalid input! Please use a numeric value between 1 and 5.");
if(debug == true)
e.printStackTrace();
input.nextLine();
}
}while(!mainCheck);
switch(menuChoice) {
case 1:
System.out.println("Please enter your fist name: ");
input.nextLine();
String loginFName = input.nextLine();
while(loginFName.matches("[a-zA-Z]*") == false) {
System.out.println("Invalid input. First name needs to be all letters. Please try again.");
loginFName = input.nextLine();
}
System.out.println("Please enter your last name: ");
String loginLName = input.nextLine();
while(loginLName.matches("[a-zA-Z]*") == false) {
System.out.println("Invalid input. Last name needs to be all letters. Please try again.");
loginLName = input.nextLine();
}
final String searchFName = loginFName;
final String searchLName = loginLName;
int loginValidation = 0;
Optional<Client> queryResult = clientArr.stream().filter(value -> value.getFName().equals(searchFName)
&&value.getLName().equals(searchLName)).findFirst();
if(queryResult.isPresent()) {
System.out.println("User "+loginFName+" "+loginLName+" successfully logged into. Welcome back to Java World Bank.");
menuChoice = 5;
}
else
System.out.println("Login failed. Returning to main menu.");
break;
case 2:
System.out.println("Clients of Java World Bank, sorted by last name: ");
clientArr.sort( (p1, p2) -> p1.getLName().compareTo(p2.getLName()) );
for(Client client : clientArr)
System.out.println(client);
menuChoice = 5;
break;
case 3:
System.out.println("Clients of Java World Bank, sorted by ID: ");
clientArr.sort( (p1, p2) -> Integer.compare(p1.getAccount().getID(),
p2.getAccount().getID()));
for(Client client : clientArr)
System.out.println(client);
menuChoice = 5;
break;
case 4:
System.out.println("You are now creating a new client account with Java World Bank!");
System.out.println("Some information is required to create this account.");
System.out.println("What would you like your ID number to be? It must contain only integers.");
check = false;
do {
try {
System.out.println("Please enter your choice: ");
idNumber = input.nextInt();
check = true;
}
catch(InputMismatchException e) {
System.out.println("ERROR: ID must contain integers only!");
input.nextLine();
}
}while(!check);
startingBalance = 0;
check = false;
// Continiously prompts user to enter valid input
do {
try {
System.out.println("What will be your starting balance?");
startingBalance = input.nextDouble();
check = true;
}
// Checks if user enters a value that is not a double
catch (InputMismatchException e) {
System.out.println("Invalid input! Please enter a numeric value.");
input.nextLine();
if(debug == true)
e.printStackTrace();
}
}while(!check);
customerAccount = new Client(idNumber, startingBalance);
System.out.println("Please enter client's first name: ");
firstName = input.nextLine();
customerAccount.setFName(firstName);
// Verifies first name is only letters, either capital or lowercase
while(firstName.matches("[a-zA-Z]*") == false) {
System.out.println("Invalid input. First name needs to be all letters. Please try again.");
firstName = input.nextLine();
customerAccount.setFName(firstName);
}
System.out.println("Please enter client's last name: ");
lastName = input.nextLine();
customerAccount.setLName(lastName);
// Verifies last name is only letters, either capital or lowercase
while(lastName.matches("[a-zA-Z]*") == false) {
System.out.println("Invalid input. Last name needs to be all letters. Please try again.");
lastName = input.nextLine();
customerAccount.setLName(lastName);
}
System.out.println("Please enter client's email address: ");
emailAddress = input.nextLine();
customerAccount.setEmail(emailAddress);
// Verifies email address only uses lowercase/capital letters, dot, underscore, and/or dashes followed by @ symbol to specify domain
while(emailAddress.matches("^[A-Za-z0-9+_.-]+@(.+)$") == false) {
System.out.println("Invalid input. Email not in valid format. Please try again.");
emailAddress = input.nextLine();
customerAccount.setEmail(emailAddress);
}
System.out.println("Please enter client's phone number: ");
phoneNumber = input.nextLine();
// Verifies phone number follows valid North American format 000-000-0000
while(phoneNumber.matches("[0-9]\\d{2}-[0-9]\\d{2}-\\d{4}") == false) {
System.out.println("Invalid input. Phone number must be in the following format: 123-456-7890. Please try again.");
phoneNumber = input.nextLine();
customerAccount.setPNumber(phoneNumber);
}
// Verifies that the starting balance the user inputs is positive
while(startingBalance < 0) {
System.out.println("**********************************");
System.out.println("ERROR: You can not start with a negative balance.");
System.out.println("Please enter a POSITIVE value for your starting balance: ");
startingBalance = input.nextDouble();
}
}//end switch
}
// Debugging to verify user input is correctly stored
if(debug == true) {
System.out.println(customerAccount.toString());
Account testing = customerAccount.getAccount();
System.out.println("ID: "+testing.getID()+ " Balance: "+testing.getBalance());
}
System.out.println("********************************");
System.out.println("Your account has been fully initialized! Thank you for choosing Java World Bank!");
System.out.println("********************************");
// Loops through menu prompt until user enters 4 to quit
int choice = 0;
while(choice != 4) {
System.out.println("Client Menu");
System.out.println("[1] Check Balance");
System.out.println("[2] Withdraw");
System.out.println("[3] Deposit");
System.out.println("[4] Exit");
System.out.println("=================================");
// Continiously prompts user to enter valid input
check = false;
do {
try {
System.out.println("So... What do you want to do?");
choice = input.nextInt();
check = true;
}
// Checks if user enters an unexpected input (not a digit)
catch(InputMismatchException e) {
System.out.println("Invalid input! Please use a numeric value between 1 and 4.");
if(debug == true)
e.printStackTrace();
input.nextLine();
}
}while(!check);
double amount = 0;
switch(choice) {
// Will display updated balance
case 1:
System.out.println("Your current balance is: $"+customerAccount.getAccount().getBalance());
System.out.println("********************************");
break;
// Allows user to withdraw money from current balance
case 2:
// Continiously prompts user to enter valid input
check = false;
do {
try {
System.out.println("How much do you wish to withdraw?");
amount = input.nextDouble();
customerAccount.getAccount().withdraw(amount); // Passes withdraw value to Account class
System.out.println("********************************");
check = true;
}
// Validates that customer has enough money to withdraw the specified amount
catch(OutOfMoney error) {
System.out.println("You do not have enough funds to do this.");
System.out.println("********************************");
}
// Validates that customer enters expected input
catch(InputMismatchException e) {
System.out.println("INVALID INPUT. Please enter a numeric value.");
// Used to clear input buffer after catching exception
input.nextLine();
System.out.println("********************************");
}
}while(!check);
// Debugging to make sure values are correctly calculated
if(debug == true)
System.out.println(customerAccount.getAccount().getBalance());
break;
// Allows user to deposit money to current balance
case 3:
check = false;
do {
try {
System.out.println("How much do you wish to deposit?");
amount = input.nextDouble();
customerAccount.getAccount().deposit(amount); // Passes deposit value to Account class
System.out.println("********************************");
check = true;
}
// Validates that user enters expected input
catch(InputMismatchException e) {
System.out.println("Invalid input. Please enter a numeric value.");
// Used to clear input buffer after catching exception
input.nextLine();
System.out.println("********************************");
}
}while(!check);
// Debugging to make sure values are correctly calculated
if(debug == true)
System.out.println(customerAccount.getAccount().getBalance());
break;
// Exits program
case 4:
System.out.println("Thank you for choosing Java World Bank!");
break;
// Checks if user does not enter 1, 2, 3, or 4 in main menu prompt
default:
System.out.println("You have entered an invalid input. Please try again.");
System.out.println("********************************");
break;
}
}
input.close();
}
}
答案 0 :(得分：2)
由于对象的初始化发生在一个条件下，编译器无法确定它是否已初始化，因此你需要确保它在条件之外初始化，例如使其为空。
using System;
using System.Web.Http;
using System.Web.Mvc;
using Umbraco.Web;
namespace Foo
{
public class WebsiteUmbracoApplication : UmbracoApplication
{
protected override void OnApplicationStarted(object sender, EventArgs e)
{
base.OnApplicationStarted(sender, e);
ConfigureDependencyInjection();
ConfigureFormatters();
}
private static void ConfigureDependencyInjection()
{
var container = UnityConfig.ConfiguredContainer;
// MVC
DependencyResolver.SetResolver(new Microsoft.Practices.Unity.Mvc.UnityDependencyResolver(container));
// Web API
GlobalConfiguration.Configuration.DependencyResolver = new Unity.WebApi.UnityDependencyResolver(container);
}
private static void ConfigureFormatters()
{
var formatters = GlobalConfiguration.Configuration.Formatters;
formatters.Remove(formatters.XmlFormatter);
}
}
}
答案 1 :(得分：2)
首先，您可能希望在此处看到有关声明和初始化变量的信息：here
您在此行初始化customerAccount：customerAccount = new Client(idNumber, startingBalance);
但是，这种情况发生在案例4中的交换机中。然后在此行System.out.println(customerAccount.toString());上，您尝试访问customerAccount的toString函数。由于此步骤不是4，因此可能无法初始化customerAccount。
考虑switch语句没有转到4并且debug设置为true的情况。 customerAccount将从此行声明：Client customerAccount;但是，代码路径不会以任何方式初始化它，因此您无法在其上调用toString。
一种解决方案可能是在您声明customerAccount或null时将其初始化为new Client()，或者仅在初始化后尝试访问此变量。很难确定没有看到Client类。
请注意，在null情况下，您可能必须执行一些空检查，例如，如果customerAccount为null，则customerAccount.toString（）将引发异常。