如何在没有不必要的十进制 0 的情况下很好地将浮点数格式化为字符串 [英] How to nicely format floating numbers to string without unnecessary decimal 0's

问题描述

一个 64 位的 double 可以精确地表示整数 +/- 2⁵³.

鉴于这个事实，我选择使用 double 类型作为我所有类型的单一类型，因为我的最大整数是一个无符号的 32 位数字.

但现在我必须打印这些伪整数，但问题是它们也与实际的双精度混合在一起.

那么如何在 Java 中很好地打印这些双打?

我已经尝试过 String.format("%f", value)，它很接近，只是我得到了很多小值的尾随零.

这是 %f

的示例输出<前>232.000000000.180000000001237875192.04.58000000000.000000001.23450000

我想要的是:

<前>2320.1812378751924.5801.2345

当然，我可以编写一个函数来修剪这些零，但是由于字符串操作，性能损失很大.我可以用其他格式的代码做得更好吗?

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Tom E. 和 Jeremy S. 的答案是不可接受的，因为他们都任意四舍五入到小数点后两位.回答前请先了解问题.

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请注意 String.format(format, args...) 是 locale-dependent(见下面的答案).

解决方案

如果想法是打印作为双精度数存储的整数，就好像它们是整数一样，否则打印双精度数:

public static String fmt(double d){if(d == (long) d)return String.format("%d",(long)d);别的return String.format("%s",d);}

产生:

2320.1812378751924.5801.2345

并且不依赖字符串操作.

A 64-bit double can represent integer +/- 2⁵³ exactly.

Given this fact, I choose to use a double type as a single type for all my types, since my largest integer is an unsigned 32-bit number.

But now I have to print these pseudo integers, but the problem is they are also mixed in with actual doubles.

So how do I print these doubles nicely in Java?

I have tried String.format("%f", value), which is close, except I get a lot of trailing zeros for small values.

Here's an example output of of %f

232.00000000
0.18000000000
1237875192.0
4.5800000000
0.00000000
1.23450000

What I want is:

232
0.18
1237875192
4.58
0
1.2345

Sure I can write a function to trim those zeros, but that's lot of performance loss due to string manipulation. Can I do better with other format code?

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The answers by Tom E. and Jeremy S. are unacceptable as they both arbitrarily rounds to two decimal places. Please understand the problem before answering.

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Please note that String.format(format, args...) is locale-dependent (see answers below).

解决方案

If the idea is to print integers stored as doubles as if they are integers, and otherwise print the doubles with the minimum necessary precision:

public static String fmt(double d)
{
    if(d == (long) d)
        return String.format("%d",(long)d);
    else
        return String.format("%s",d);
}

Produces:

232
0.18
1237875192
4.58
0
1.2345

And does not rely on string manipulation.

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