通过用户输入指定精确的小数位数，Java
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Specify exact number of decimal places by user input , Java
提问by Adam Beňko
I am writing a calculator program, where the user in the last input prompt writes the number of decimal points (1, 2 ,3...), that the output of for example sum of 2 numbers should have.
我正在编写一个计算器程序，用户在最后一个输入提示中写下小数点的数量（1、2、3...），例如 2 个数字之和的输出应该有。
import java.util.Scanner;
import java.util.Formatter;
public class Lab01 {
public void start(String[] args) {
double cislo1;
double cislo2;
int operacia;
String decimal;
String dec;
Scanner op = new Scanner(System.in);
System.out.println("Select operation (1-sum, 2-dev, 3- *, 4- / )");
operacia = op.nextInt();
if (operacia >= 1 && operacia <= 4) {
if(operacia == 1) {
Scanner input = new Scanner(System.in);
System.out.println("Enter number one:");
cislo1=input.nextDouble();
System.out.println("Enter number two:");
cislo2=input.nextDouble();
System.out.println("Enter number of decimal points");
decimal=input.nextLine();
dec="%."+decimal+"f";
Formatter fmt = new Formatter();
fmt.format(dec, cislo2);
System.out.println( fmt);
}
} else {
System.out.println("wrong!");
}
}
}
I have tried Formatter method for the decimal input but the error says" Conversion = '.' "
我已经尝试了十进制输入的 Formatter 方法，但错误显示“Conversion = '.' ”
System.out.println("Enter number of decimal points");
decimal = input.nextLine();
dec = "%." + decimal + "f";
Formatter fmt = new Formatter();
fmt.format(dec, cislo2);
System.out.println(fmt);
采纳答案by Bernardo Rocha
Your variable decimalshould be an int. So you should change the follow lines:
你的变量decimal应该是一个整数。所以你应该改变以下几行：
String decimal;
You should change to:
你应该改为：
int decimal;
And:
和：
decimal = input.nextLine();
You should change to:
你应该改为：
decimal = input.nextInt();
Or, if you want to keep it as a String, you can add an extra input.nextLine();before reading the number of decimals. It occurs because nextLine() consumes the line separator where you are reading your cislo2variable and nextInt()will only read an int.
或者，如果您想将其保留为字符串，则可以input.nextLine();在读取小数位数之前添加额外内容。发生这种情况是因为 nextLine() 消耗了您正在读取cislo2变量的行分隔符，并且nextInt()只会读取一个 int。
