这是我的Java 1决赛。如果余额低于0美元（并且没有创建对象动作 - 这将被添加到arraylist行动中），我希望它反对说资金不足。
我相信我会在2个地方使用条件。一个在Account类的getDouble（）方法中，以及在Action类的对象Action（）中。也许在主要的方法中......我也不知道我会放置什么条件，并且以最简单的方式不会弄乱我的程序..
我还有一个单独的问题......
如果我做了一个很大的数字，比如7或8位数，它会返回一个不同的值，比如200E7JK（例子）。我认为双重达到某种最大值。我该如何解决这个问题？
主要课程：
公共类ATM_Larrabee {public static void main(String[] args) {
Scanner in = new Scanner(System.in);
ArrayList<Action> actions = new ArrayList();
Account acc = new Account("N/A", "N/A", 0.0);
acc.displayWelcome();
acc.createUsernamePassword();
boolean options = true;
while(options){
acc.disconnect();
System.out.println("\nWhat action would you like to take?");
System.out.println("[ Account Balance: $" + Account.balance + " ]");
System.out.println("\n- Type 'deposit' to make a deposit into your account.");
System.out.println("- Type 'withdrawal' to make a withdrawal from your account.");
System.out.println("- Type 'history' to see your history of transactions.");
System.out.println("- Type 'exit' if you are finished.\n");
String input = in.nextLine();
if("exit".equals(input)){
break;
}
if("history".equals(input)){
Action actCopy = new Action("N/A", 0);
System.out.println("\nBelow is a history of all transactions made:\n");
for(int x = 0; x < actions.size(); x++){
actCopy = actions.get(x);
System.out.println(actCopy.getType() + ": $" + actCopy.getAmount());
}
}
if("deposit".equals(input) || "withdrawal".equals(input)){
double actionAmount;
actionAmount = acc.getDouble();
Action act = new Action(input, actionAmount);
actions.add(act);
System.out.println("\nAction accepted.");
}
}
System.out.println("\nYour Account Balance Is: $" + Account.balance);
System.out.println("\nThank you for using Really Boring Bank!");
}
}
帐户类：
public class Account {
Scanner in = new Scanner(System.in);
static String username = "n/a";
static String password = "n/a";
static double balance = 0.0;
public Account(String u, String p, double b){
username = u;
password = p;
balance = b;
}
public void displayWelcome(){
String[] welcome = new String[3];
welcome[0] = "Welcome to Really Boring Banking!";
welcome[1] = "Hi there! Welcome to Really Boring Banking!";
welcome[2] = "Hello! Welcome to Really Boring Banking!";
Random rand = new Random();
int r = rand.nextInt(3);
if(r == 0){
System.out.println(welcome[0]);
}
if(r == 1){
System.out.println(welcome[1]);
}
if(r == 2){
System.out.println(welcome[2]);
}
}
public void createUsernamePassword(){
System.out.println("\nAs a new member, you will first need to create a username and password.");
System.out.println("\n[ Enter a username for your account: ]");
String input = in.nextLine();
setUsername(input);
System.out.println("\n[ Enter a password for your account: ]");
input = in.nextLine();
setPassword(input);
}
public void disconnect(){
Random rand = new Random();
int r = rand.nextInt(5);
if(r == 1){
System.out.println("\n[ Connection to server lost. Please log back into your account. ]");
boolean loggedIn = false;
boolean correctUsername = false;
boolean correctPassword = false;
while(!loggedIn){
while(!correctUsername){
System.out.println("\n[ Enter username: ]");
String input = in.nextLine();
if(Account.username.equals(input)){
correctUsername = true;
System.out.println("\nUsername Accepted");
}
else{
System.out.println("[ Incorrect username. Please try again. ] ");
}
}
while(!correctPassword){
System.out.println("\n[ Enter password: ]");
String input = in.nextLine();
if(Account.password.equals(input)){
correctPassword = true;
System.out.println("\nPassword Accepted");
loggedIn = true;
System.out.println("\nSuccessfully logged back into account: "+ Account.username + ".");
}
else{
System.out.println("[ Incorrect password. Please try again. ] ");
}
}
}
}
}
public double getDouble(){
boolean validInput = false;
double doub = 0.0;
while (!validInput) {
System.out.println("\n[ Please enter an amount: ]\n");
String input = in.nextLine();
try {
doub = Double.parseDouble(input);
validInput = true;
} catch (NumberFormatException e) {
validInput = false;
}
}
return doub;
}
public String getUsername(){
return Account.username;
}
public void setUsername(String u){
username = u;
}
public String getPassword(){
return Account.password;
}
public void setPassword(String p){
password = p;
}
public double getBalance(){
return Account.balance;
}
public void setSeed(double b){
balance = b;
}
}
动作类：
public class Action {
double amount = 0;
String type;
// object for withdrawals and deposits (saved into an arraylist elsewhere)
public Action(String t, double a){
type = t;
amount = a;
if("deposit".equals(type)){
type = "deposit";
Account.balance = Account.balance + a;
}
if("withdrawal".equals(type)){
type = "withdrawal";
Account.balance = Account.balance - a;
}
}
// gets and sets
public String getType(){
return this.type;
}
public void setType(String t){
type = t;
}
public double getAmount(){
return this.amount;
}
public void setAmount(double a){
amount = a;
}
}
答案 0 :(得分：0)
在balance中制作static（和其他字段）Account会使所有内容都变为全局（并且意味着您只能拥有一个Account）。但是，在你的问题的背景下，
Account.balance = Account.balance - a;
需要进行测试以确保a不大于Account.balance
if (Account.balance >= a) {
// Account.balance = Account.balance - a;
Account.balance -= a;
} else {
System.err.printf("%d is greater than %d and would be an overdraft%n",
a, Account.balance);
}
从长远来看，虽然您需要Account的实例（因此请将它们作为实例字段并创建Account的实例）。