我需要能够捕获小数点后只有 2 位数字的小数 java，试过这个

Question

我需要能够捕获小数点后只有 2 位的小数

点java，试过这个

这是我的代码，我需要知道能够读取小数点后两位

package project.pkg1;

import javax.swing.JOptionPane;

/**
 * @author Maria Andrea Quintana 4891405 *
 * @author Salvador Frias
 */
public class Project1 {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here

        String s1 = JOptionPane.showInputDialog("Enter the purchase amount");


        if (s1 == null) {
            JOptionPane.showMessageDialog(null, "You must enter a valid integer");
            System.exit(0);
        }

        if (s1.isEmpty()) {
            JOptionPane.showMessageDialog(null, "You must enter a valid integer");
            System.exit(0);
        }

        for (int i = 0; i < s1.length(); i = i + 1) {
            if (!Character.isDigit(s1.charAt(i))) {
                JOptionPane.showMessageDialog(null, "You must enter an integer value");
                System.exit(0);
            }
        }

Answer 1

您可以使用 DecimalFormat 来格式化您的双精度：

    double input = 455.1689;

    DecimalFormat df = new DecimalFormat("#.00");

    System.out.println(df.format(input));

看看this question处理同样的问题。

编辑 2：
删除 for 循环并将此代码放在原处

    double input = Double.parseDouble(s1);
    DecimalFormat df = new DecimalFormat("#.00");

    s1 = df.format(input);

Answer 2

这样试试：

s1 是您的文本或字符串值：

   String s=String.format("output: %.2f", s1);
                System.out.println(s);

Answer 3

因为你工作的钱可能不同currency unit's. I would suggest you to take a look at Moneta API

要添加的 Maven 依赖项：

<!-- Moneta -->
<dependency>
   <groupId>org.javamoney</groupId>
      <artifactId>moneta</artifactId>
    <version>0.9</version>
</dependency>

示例：

MonetaryAmount monetaryAmount = MonetaryAmounts.getDefaultAmountFactory()
.setNumber(3.45)
.setCurrency("USD")
.create();

System.out.println("EXACT MONETARY VALUE: "+monetaryAmount.getNumber().doubleValueExact()); // 3.45
System.out.println("VALUE AFTER DECIMAL: "+monetaryAmount.getNumber().getAmountFractionNumerator()); // 45

编辑：

如果你被允许使用regular expressions，我想这就是你要找的

String s1 = JOptionPane.showInputDialog("Enter the purchase amount");
double d = 0.0;

int counter = 0;
Matcher match = Pattern.compile("[aA-zZ]+").matcher(s1);
while (match.find()) {
    counter++;
}

if((!s1.isEmpty()) && (s1.trim().length()!=0) && (counter == 0)){
    if(s1.contains(".")){
        String[] strings = s1.split("\.");
        if (strings[1].length() > 2) {
            System.out.println("Maximum 2 places allowed after decimal.");
            System.exit(0);
        }
    }
    d = Double.parseDouble(s1);
}else if(counter > 0){
    System.out.println("Only numeric values are allowed");
    System.exit(0);
}
System.out.println("Expected input retrieved: " + d);

Answer 4

已解决，

      String s1 = JOptionPane.showInputDialog("Enter the purchase amount");

    if (s1 == null) {
        JOptionPane.showMessageDialog(null, "You must enter a valid integer");
        System.exit(0);
    }

    if (s1.isEmpty()) {
        JOptionPane.showMessageDialog(null, "You must enter a valid integer");
        System.exit(0);
    }

    if (s1.equals("0")) {
        JOptionPane.showMessageDialog(null, "You must enter a valid integer");
        System.exit(0);
    }

    if (s1.matches("[a-zA-Z]+")) {
        JOptionPane.showMessageDialog(null, "You must enter a valid integer");
        System.exit(0);
    }

    double input = Double.parseDouble(s1);
    DecimalFormat df = new DecimalFormat("#.00");

    s1 = df.format(input);

我需要能够捕获小数点后只有 2 位数字的小数 java，试过这个

I need to be able to capture decimals with only 2 digits after the decimal point java, tried this

java

floating-point

double

int

decimal

要添加的 Maven 依赖项：

示例：

编辑：