将字符串转换为Java中2位小数的十进制数 [英] Convert string to decimal number with 2 decimal places in Java

问题描述

在Java中，我试图将一个格式为###。##的字符串解析为一个浮点数。即使字符串的值 123.00 ，浮动也应该是2个小数位。 123.00 ，而不是 123.0 。

这是我到目前为止：

  System.out.println（字符串的汽油放入喜好是+ stringLitersOfPetrol）; 
 
 Float litersOfPetrol = Float.parseFloat（stringLitersOfPetrol）; 
 
 DecimalFormat df = new DecimalFormat（0.00）; 
 df.setMaximumFractionDigits（2）; 
 
 litersOfPetrol = Float.parseFloat（df.format（litersOfPetrol））; 
 
 System.out.println（放入编辑器前的汽油升数+ litersOfPetrol）; 
  

打印：

 在放入编辑器之前，汽油的字符串升为010.00 
升汽油：10.0 
  

  litersOfPetrol = Float  
 
 .parseFloat（df.format（litersOfPetrol））; 
  

在这里，您将float设置为字符串，但是随后该字符串再次转换为浮动，然后你在标准输出是你的浮法，得到了一个标准的格式。看看这段代码

  import java.text.DecimalFormat; 
 
 String stringLitersOfPetrol =123.00; 
 System.out.println（字符串的汽油放入喜好是+ stringLitersOfPetrol）; 
 Float litersOfPetrol = Float.parseFloat（stringLitersOfPetrol）; 
 DecimalFormat df = new DecimalFormat（0.00）; 
 df.setMaximumFractionDigits（2）; 
 stringLitersOfPetrol = df.format（litersOfPetrol）; 
 System.out.println（放入编辑器之前的汽油升数+ stringLitersOfPetrol）; 
  

顺便说一下，当你想使用小数时，忘记double和float的存在建议只使用BigDecimal对象，它会为您节省很多头痛。

In Java, I am trying to parse a string of format "###.##" to a float. The string should always have 2 decimal places.

Even if the String has value 123.00, the float should also be 123.00, not 123.0.

This is what I have so far:

System.out.println("string liters of petrol putting in preferences is " + stringLitersOfPetrol);

Float litersOfPetrol = Float.parseFloat(stringLitersOfPetrol);

DecimalFormat df = new DecimalFormat("0.00");
df.setMaximumFractionDigits(2);

litersOfPetrol = Float.parseFloat(df.format(litersOfPetrol));

System.out.println("liters of petrol before putting in editor: " + litersOfPetrol);

It prints:

string liters of petrol putting in preferences is 010.00 
liters of petrol before putting in editor: 10.0

解决方案

This line is your problem:

litersOfPetrol = Float.parseFloat(df.format(litersOfPetrol));

There you formatted your float to string as you wanted, but but then that string got transformed again to a float, and then what you printed in stdout was your float that got a standard formatting. Take a look at this code

import java.text.DecimalFormat;

String stringLitersOfPetrol = "123.00";
System.out.println("string liters of petrol putting in preferences is "+stringLitersOfPetrol);
Float litersOfPetrol=Float.parseFloat(stringLitersOfPetrol);
DecimalFormat df = new DecimalFormat("0.00");
df.setMaximumFractionDigits(2);
stringLitersOfPetrol = df.format(litersOfPetrol);
System.out.println("liters of petrol before putting in editor : "+stringLitersOfPetrol);

And by the way, when you want to use decimals, forget the existence of double and float as others suggested and just use BigDecimal object, it will save you a lot of headache.

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