問(wèn)題描述

我有一個(gè)非常煩人的問(wèn)題，即 Java 中的浮點(diǎn)數(shù)或雙精度數(shù)很長(zhǎng).基本上這個(gè)想法是，如果我執(zhí)行:

I have a very annoying problem with long sums of floats or doubles in Java. Basically the idea is that if I execute:

for ( float value = 0.0f; value < 1.0f; value += 0.1f )
    System.out.println( value );

我得到的是:

0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.70000005
0.8000001
0.9000001

我知道有浮動(dòng)精度誤差的累積，但是，如何擺脫這個(gè)?我嘗試使用 doubles 將錯(cuò)誤減半，但結(jié)果還是一樣.

I understand that there is an accumulation of the floating precision error, however, how to get rid of this? I tried using doubles to half the error, but the result is still the same.

有什么想法嗎?

推薦答案

沒(méi)有將 0.1 精確表示為 float 或 double.由于這種表示錯(cuò)誤，結(jié)果與您的預(yù)期略有不同.

There is a no exact representation of 0.1 as a float or double. Because of this representation error the results are slightly different from what you expected.

您可以使用的幾種方法:

A couple of approaches you can use:

• 當(dāng)使用 double 類型時(shí)，只顯示你需要的數(shù)字.在檢查相等性時(shí)，無(wú)論哪種方式都允許有一個(gè)小的容差.
• 或者使用允許您存儲(chǔ)要精確表示的數(shù)字的類型，例如 BigDecimal 可以精確表示 0.1.

• When using the double type, only display as many digits as you need. When checking for equality allow for a small tolerance either way.
• Alternatively use a type that allows you to store the numbers you are trying to represent exactly, for example BigDecimal can represent 0.1 exactly.

BigDecimal 的示例代碼:

BigDecimal step = new BigDecimal("0.1");
for (BigDecimal value = BigDecimal.ZERO;
     value.compareTo(BigDecimal.ONE) < 0;
     value = value.add(step)) {
    System.out.println(value);
}

在線查看:ideone

這篇關(guān)于如何避免 Java 中的浮點(diǎn)數(shù)或雙精度數(shù)的浮點(diǎn)精度錯(cuò)誤?的文章就介紹到這了，希望我們推薦的答案對(duì)大家有所幫助，也希望大家多多支持html5模板網(wǎng)！