在Java中浮点数的精度错误 [英] Precision error with floats in Java

问题描述

我想知道在Java中解决精确错误的最佳方法是什么。正如你在下面的例子中看到的那样，有一些精确的错误：

$ p $ class FloatTest
{
public static void main（String [] args）
{
Float number1 = 1.89f;

（int i = 11; i <800; i * = 2）
{
System.out.println（loop value：+ i）;
System.out.println（i * number1）;
System.out.println（）;





$ p $显示的结果是： / p>

循环值：11

20.789999

循环值：22

41.579998

循环值：44

b
$ b 83.159996

循环值：88

166.31999

循环值：176

332.63998

循环值：352

665.27997

循环值：704

1330.5599

另外，如果有人可以解释为什么它只能从11开始，每次翻倍。我认为所有其他值（或至少是其中的许多值）显示正确的结果。

以前的这样的问题使我头痛，我通常使用数字格式化程序或把它们放到一个字符串中。

编辑：正如人们提到的，我可以使用double，但是尝试之后，似乎1.89作为一个双倍的792仍然输出一个错误（输出是1496.8799999999999）。

我想我会尝试其他解决方案，如BigDecimal

$ b $如果你真的关心精度，你应该使用BigDecimal

http://download.oracle.com/javase/1.5.0/docs /api/java/math/BigDecimal.html

I'm wondering what the best way to fix precision errors is in Java. As you can see in the following example, there are precision errors:

class FloatTest
{
  public static void main(String[] args)
  {
    Float number1 = 1.89f;

    for(int i = 11; i < 800; i*=2)
    {
      System.out.println("loop value: " + i);
      System.out.println(i*number1);
      System.out.println("");
    }
  }
}

The result displayed is:

loop value: 11

20.789999

loop value: 22

41.579998

loop value: 44

83.159996

loop value: 88

166.31999

loop value: 176

332.63998

loop value: 352

665.27997

loop value: 704

1330.5599

Also, if someone can explain why it only does it starting at 11 and doubling the value every time. I think all other values (or many of them at least) displayed the correct result.

Problems like this have caused me headache in the past and I usually use number formatters or put them into a String.

Edit: As people have mentioned, I could use a double, but after trying it, it seems that 1.89 as a double times 792 still outputs an error (the output is 1496.8799999999999).

I guess I'll try the other solutions such as BigDecimal

解决方案

If you really care about precision, you should use BigDecimal

http://download.oracle.com/javase/1,5.0/docs/api/java/math/BigDecimal.html

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