现在的问题是，如果你在输出时运行我的程序，我应该有一个字符串输出用户输入的每月投资、利率和年份，它应该在一行和下一行打印它，之后应该是相同的，但是如果用户输入了不同的值，他想为每月投资、利率和年份输入另一个不同的值。我的可能是它把所有东西都打印成一个像 ex:$400 2.0% 3 $500 3.0% 2 <--- 这从 $500 开始应该在下一行而不是第一个条目的第一个？
System.out.print("Inv/Mo.\tRate\tYears\tFuture Value\n");
for (int j = 0; j < FutureValueArrayList.size(); j++)
{
String myArrayList = FutureValueArrayList.get(j);
System.out.print(ArrayList + "\t");
System.out.println();
}
我也得到这个错误我似乎无法找到解决它的方法“线程主在调用 println() 之前停止”这是 print(ArrayList + "\t") 之后的 println；在我的 for 循环中。
import java.util.*;
import java.text.*;
public class FutureValueApp
{
public static void main(String[] args)
{
// display a welcome message
System.out.println("Welcome to the Future Value Calculator");
System.out.println();
ArrayList<String> FutureValueArrayList = new ArrayList<String>();
// perform 1 or more calculations
Scanner sc = new Scanner(System.in);
String choice = "y";
while (choice.equalsIgnoreCase("y"))
{
// get the input from the user
System.out.println("DATA ENTRY");
double monthlyInvestment = getDoubleWithinRange(sc,
"Enter monthly investment: ", 0, 1000);
double interestRate = getDoubleWithinRange(sc,
"Enter yearly interest rate: ", 0, 30);
int years = getIntWithinRange(sc,
"Enter number of years: ", 0, 100);
// calculate the future value
double monthlyInterestRate = interestRate/12/100;
int months = years * 12;
double futureValue = calculateFutureValue(
monthlyInvestment, monthlyInterestRate, months);
// get the currency and percent formatters
NumberFormat currency = NumberFormat.getCurrencyInstance();
NumberFormat percent = NumberFormat.getPercentInstance();
percent.setMinimumFractionDigits(1);
// format the result as a single string
String results =
"Monthly investment:\t"
+ currency.format(monthlyInvestment) + "\n"
+ "Yearly interest rate:\t"
+ percent.format(interestRate/100) + "\n"
+ "Number of years:\t"
+ years + "\n"
+ "Future value:\t\t"
+ currency.format(futureValue) + "\n";
// print the results
System.out.println();
System.out.println("FORMATTED RESULTS");
System.out.println(results);
String monthlyInvestmentFormat = currency.format(monthlyInvestment);
String interestRateFormat = percent.format(interestRate/100);
String futureValueFormat = currency.format(futureValue);
FutureValueArrayList.add(monthlyInvestmentFormat);
FutureValueArrayList.add(interestRateFormat);
FutureValueArrayList.add(Integer.toString(years));
FutureValueArrayList.add(futureValueFormat);
// see if the user wants to continue
System.out.print("Continue? (y/n): ");
choice = sc.next();
System.out.println();
}
System.out.print("Inv/Mo.\tRate\tYears\tFuture Value\n");
for (int j = 0; j < FutureValueArrayList.size(); j++)
{
String ArrayList = FutureValueArrayList.get(j);
System.out.print(ArrayList + "\t");
System.out.println();
}
System.out.println();
}
public static double getDouble(Scanner sc, String prompt)
{
boolean isValid = false;
double d = 0;
while (isValid == false)
{
System.out.print(prompt);
if (sc.hasNextDouble())
{
d = sc.nextDouble();
isValid = true;
}
else
{
System.out.println("Error! Invalid decimal value. Try again.");
}
sc.nextLine(); // discard any other data entered on the line
}
return d;
}
public static double getDoubleWithinRange(Scanner sc, String prompt,
double min, double max)
{
double d = 0;
boolean isValid = false;
while (isValid == false)
{
d = getDouble(sc, prompt);
if (d <= min)
System.out.println(
"Error! Number must be greater than " + min + ".");
else if (d >= max)
System.out.println(
"Error! Number must be less than " + max + ".");
else
isValid = true;
}
return d;
}
public static int getInt(Scanner sc, String prompt)
{
boolean isValidInt = false;
int i = 0;
while (isValidInt == false)
{
System.out.print(prompt);
if (sc.hasNextInt())
{
i = sc.nextInt();
isValidInt = true;
}
else
{
System.out.println("Error! Invalid integer value. Try again.");
}
sc.nextLine(); // discard any other data entered on the line
}
return i;
}
public static int getIntWithinRange(Scanner sc, String prompt,
int min, int max)
{
int i = 0;
boolean isValid = false;
while (isValid == false)
{
i = getInt(sc, prompt);
if (i <= min)
System.out.println(
"Error! Number must be greater than " + min + ".");
else if (i >= max)
System.out.println(
"Error! Number must be less than " + max + ".");
else
isValid = true;
}
return i;
}
public static double calculateFutureValue(double monthlyInvestment,
double monthlyInterestRate, int months)
{
double futureValue = 0;
for (int i = 1; i <= months; i++)
{
futureValue =
(futureValue + monthlyInvestment) *
(1 + monthlyInterestRate);
}
return futureValue;
}
}