我已经添加了我的整个代码来澄清，我的问题不是错过了＆＃34; println＆＃34;好像很多人在我下面的代码中建议我的问题，我要求用户输入每月投资，年利率和年数，然后问他们是否要继续添加另一个月投资，年利率和年，直到他们说不之后我想要显示它。问题是，每当他们对输入更多数据说“是”时，它应该在第二行中显示该日期，在程序结束时显示该日期，或者他们拒绝继续，而只是将所有内容显示在一行中。
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>(4);
// 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 i = 0; i < FutureValueArrayList.size(); i++)
{
System.out.print(FutureValueArrayList + "\n");
}
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;
}
}
我的for循环给了我这样的输出粗体是当用户输入yes以输入更多数据时它应该在第二行而不是与他们第一次输入数据时一起：
$ 100.00 2.0％2 $ 2,450.64 $ 150.00 2.0％2 $ 36,420.71
答案 0 :(得分：3)
你在哪里使用System.out.print()，它会在没有\n分隔符的情况下打印1行。
使用System.out.println()会自动将\n分隔符放在字符串的末尾。
\n是新的行分隔符。
\t是制表符分隔符。
编辑：我认为您正在尝试标记每个输出。 （因为第一个印刷声明）
如果是这样，你就不能使用for循环（技术上）。主要是因为循环不知道哪个标签属于哪个元素/索引。
如果您知道哪个元素将存储哪些数据只是手动标记它们
关于您的评论System.out.println（“Rate：”+ FutureValueArrayList.get（i））
//我是存储费率值的索引。
编辑。
您需要查看Formatter
示例代码 - 这将打印一个列宽为20个字符的表。
Formatter formatter = new Formatter();
System.out.println(formatter.format("%20s %20s %20s %20s %20s", "Title*", "Title*", "Title*", "Title*", "Title*"));
for (int i = 0; i < 10; i++) {
formatter = new Formatter();
String rowData = "info" + i;
System.out.println(formatter.format("%20s %20s %20s %20s %20s", rowData, rowData, rowData, rowData, rowData));
}
答案 1 :(得分：1)
您需要使用println()来显示新行中的每个条目。它将打印您的条目，然后在末尾插入行分隔符以终止该行。
System.out.println(FutureValueArray);
否则，您可以修改print()方法参数，使其在新行上打印。这样的事情： -
System.out.print(FutureValueArray + "\n");
请注意，\t表示水平制表符，而\n表示换行符。
答案 2 :(得分：1)
使用
for (int i = 0; i < FutureValueArrayList.size(); i++)
{
String FutureValueArray = FutureValueArrayList.get(i);
System.out.println(FutureValueArray + "\n");
}
println会在结尾处自动添加新行字符
“/ n”也可以用作新行字符