在 Java 中格式化小数的最佳方法是什么？

Question

I've been looking for formatting decimal numbers easily as in JavaScript by using toFixed() .

What's your suggestion?

Answer 1

Did you take a look at the BigDecimal class?? There are a number of scale related functions that might do what you need.

Answer 2

Using String.format is likely to be the simplest.

var num = new Number(13.3714);
document.write(num.toFixed()+"<br />");
document.write(num.toFixed(1)+"<br />");
document.write(num.toFixed(3)+"<br />");
document.write(num.toFixed(10));

in Java

double num = 13.3714;
// Uses String.format()
System.out.printf(
          "%f<br />" +
          "%.1f<br />" +
          "%.3f<br />" +
          "%.10f<br />", num, num, num, num);

Answer 3

将BigDecimal用于Java中与十进制相关的任何内容。

Answer 4

Best Way Depends Upon Requirement

1. Using the format() method

specifies the format "%.3f" denotes 3 decimal places "%.4f" denotes 4 decimal

for Example Double d = 32345.123214; System.out.format("%.2f", d);//output 32345.12

2. String.format

Double x = 4.0; System.out.println(String.format("%.5f", x)); //output4.00000

3. DecimalFormat DecimalFormat class has various format options to round up the decimal places based on the initialized format. In the below example, we have initialized the DecimalFormat with the format as "#.##". This means it limits the decimal place up to 2 digits

 Double d = 1234.67538911;
    DecimalFormat df = new DecimalFormat("#.##");
    
    System.out.println("Using DecimalForamt: " + df.format(d));//output 1234.67

4.Using Math.round()

The Math.round() method is another method to limit the decimal places in Java. If we want to round a number to 1 decimal place, then we multiply and divide the input number by 10.0 in the round() method. Similarly, for 2 decimal places, we can use 100.0, for 3 decimal places, we can use 1000.0, and so on.

Double n = 123.4567;
    System.out.println("Original value: " + n);
    
    Double d = (double) (Math.round(n*10.0)/10.0);
    System.out.println(d);
    
    d = (double) (Math.round(n*100.0)/100.0);
    System.out.println(d);
    
    d = (double) (Math.round(n*1000.0)/1000.0);
    System.out.println(d);


Original value: 123.4567
123.5
123.46
123.457

5.Using apache commons library apache-commons math3 library contains a Precision class method round()

 Double d = 456.98234;
    
    Double n = Precision.round(d,2);

to add library

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-math3 -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-math3</artifactId>
    <version>3.6.1</version>
</dependency>