[英]do-while loop not continuing
我的下面的代碼有問題。 一切正常,除非我希望如果用戶最后輸入“ Y”,則程序重新啟動,如果按下任何其他鍵,則程序結束。
但是,無論何時在“重新啟動計算器”提示下鍵入任何內容,無論我鍵入“ Y”還是“ N”,它都會停止運行。 在這里用Y / N驗證不是太重要,我只希望它在鍵入Y時重新啟動,而在鍵入其他任何值時結束。
對於noob代碼表示歉意,這里是Java初學者。
import java.util.Scanner;
import java.text.*;
public class Savings {
public static void main(String[] args)
{
//Imports scanner, to read user's input
Scanner input = new Scanner(System.in);
Scanner scan = new Scanner(System.in);
do {
//Asks for and receives user's initial deposit
int initial_Deposit;
do {
System.out.print("Enter initial deposit in dollars (Between $1 - $50000: ");
while (!scan.hasNextInt()) {
System.out.println("Please enter a valid number between '1-50000'");
scan.next();
}
initial_Deposit = scan.nextInt();
} while (initial_Deposit <= 0 || initial_Deposit >= 50001);
//Asks for and receives user's interest rate
double interest_Rate;
do {
System.out.print("Enter interest rate as a percentage between '0.1-100.0' (e.g. 4.0):");
while (!scan.hasNextDouble()) {
System.out.println("Enter interest rate as a percentage between '0.1-100.0' (e.g. 4.0):");
scan.next();
}
interest_Rate = scan.nextDouble();
} while (interest_Rate <= 0.0 || interest_Rate >= 100.1);
//Asks for and receives user's monthly deposit
int monthly_Deposit;
do {
System.out.print("Enter monthly deposit in dollars between '$1 - $5000: ");
while (!scan.hasNextDouble()) {
System.out.println("Enter monthly deposit in dollars between '$1 - $5000: ");
scan.next();
}
monthly_Deposit = scan.nextInt();
} while (monthly_Deposit <= 0 || monthly_Deposit >= 5001);
//Asks for and receives user's investment duration
int monthly_Duration;
do {
System.out.print("Enter investment duration (Between 1 and 12): ");
while (!scan.hasNextDouble()) {
System.out.println("Enter investment duration (Between 1 and 12): ");
scan.next();
}
monthly_Duration = scan.nextInt();
} while (monthly_Duration <= 0 || monthly_Duration >= 13);
//Asks for and receives user's first name
String first_Name;
System.out.print("Enter first name: ");
first_Name = input.next();
//Asks for and receives user's surname
String last_Name;
System.out.print("Enter surname: ");
last_Name = input.next();
//Formats first name to only first letter
char firstLetter = first_Name.charAt(0);
//Changes name to correct format
String formatted_Name;
formatted_Name = "Savings growth over the next six months for " + last_Name + ", " + firstLetter;
System.out.println(formatted_Name);
//Calculates the first balance
double balanceCurrent;
balanceCurrent = initial_Deposit + monthly_Deposit;
//Prepares to format currency
DecimalFormat df = new DecimalFormat("#.##");
//Defining variables
double balanceNew;
double interestEarned;
//Defining counter for while loop
int counter;
counter = monthly_Duration;
int month_Counter;
month_Counter = 1;
//While loop to calculate savings
while (counter > 0) {
balanceNew = balanceCurrent + (balanceCurrent *((interest_Rate /12)/100));
interestEarned = balanceCurrent *((interest_Rate /12)/100);
balanceCurrent = balanceNew + monthly_Deposit;
System.out.println("Balance after month " + month_Counter + ": $" + df.format((balanceNew)));
System.out.println("Interest earned for this month: $" + df.format(interestEarned));
counter = counter - 1;
month_Counter = month_Counter + 1;
}
//Formats data into a table
balanceCurrent = initial_Deposit + monthly_Deposit;
counter = monthly_Duration;
int month;
month = 0;
String dollarSign = "$";
String stringHeadingOne = "Month";
String stringHeadingTwo = "New Balance";
String stringHeadingThree = "Interest Earned";
String dividerOne = "----- ----------- ---------------";
System.out.println("");
System.out.printf("%-9s %s %19s \n", stringHeadingOne, stringHeadingTwo, stringHeadingThree);
System.out.println(dividerOne);
while (counter > 0) {
balanceNew = balanceCurrent + (balanceCurrent *((interest_Rate /12)/100));
interestEarned = balanceCurrent *((interest_Rate /12)/100);
balanceCurrent = balanceNew + monthly_Deposit;
month = month + 1;
System.out.printf("%-11s %s %s %13s %s \n", month, dollarSign, df.format((balanceNew)), dollarSign, df.format(interestEarned));
counter = counter - 1;
}
System.out.print("Restart Calculator? Y/N);");
} while (scan.next() == "Y");
}}
while (scan.next() == "Y"); // Is checking for reference equality
在Java中進行對象比較時,請使用equals()
while (scan.next().equals("Y"));
或者,如前一個答案所指出的,您可以使用==
運算符比較字符
嘗試這個:
scan.nextLine().charAt(0) == 'Y'
比較字符串或任何其他對象時,您需要使用.equals(Object other)方法。 您只能將==與基元(boolean,int,double,...)一起使用
scan.nextLine().equals("Y");
//or
scan.next().equals("Y");
還有一種將字符串轉換為大寫的方法,該方法允許用戶輸入“ y”或“ Y”
scan.next().toUpperCase().equals("Y");
您應該對字符串使用Equals方法:
while ("Y".equals(scan.next()));
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