问题：在Java里怎将字节数转换为我们可以读懂的格式？

在Java里怎将字节数转换为我们可以读懂的格式

像1024应该变成"1 Kb"，而1024*1024应该变成"1 Mb".

我很讨厌为每个项目都写一个工具方法。在Apache Commons有没有这样的一个静态方法呢？

回答一

有趣的事情：这里上传的源代码片段是整个Stack Overflow最多人复制的，但是是有错误的。虽然被修复了，但是已经很混乱了。

这篇文章的完整故事：在Stack Overflow被复制次数最多的代码片段是有错误的。

SI (1 k = 1,000)

public static String humanReadableByteCountSI(long bytes) {if (-1000 < bytes && bytes < 1000) {return bytes + " B";}CharacterIterator ci = new StringCharacterIterator("kMGTPE");while (bytes <= -999_950 || bytes >= 999_950) {bytes /= 1000;ci.next();}return String.format("%.1f %cB", bytes / 1000.0, ci.current());
}

Binary (1 Ki = 1,024)

public static String humanReadableByteCountBin(long bytes) {long absB = bytes == Long.MIN_VALUE ? Long.MAX_VALUE : Math.abs(bytes);if (absB < 1024) {return bytes + " B";}long value = absB;CharacterIterator ci = new StringCharacterIterator("KMGTPE");for (int i = 40; i >= 0 && absB > 0xfffccccccccccccL >> i; i -= 10) {value >>= 10;ci.next();}value *= Long.signum(bytes);return String.format("%.1f %ciB", value / 1024.0, ci.current());
}

Example output:

                              SI     BINARY0:        0 B        0 B27:       27 B       27 B999:      999 B      999 B1000:     1.0 kB     1000 B1023:     1.0 kB     1023 B1024:     1.0 kB    1.0 KiB1728:     1.7 kB    1.7 KiB110592:   110.6 kB  108.0 KiB7077888:     7.1 MB    6.8 MiB452984832:   453.0 MB  432.0 MiB28991029248:    29.0 GB   27.0 GiB1855425871872:     1.9 TB    1.7 TiB9223372036854775807:     9.2 EB    8.0 EiB   (Long.MAX_VALUE)

回答二

private String bytesIntoHumanReadable(long bytes) {long kilobyte = 1024;long megabyte = kilobyte * 1024;long gigabyte = megabyte * 1024;long terabyte = gigabyte * 1024;if ((bytes >= 0) && (bytes < kilobyte)) {return bytes + " B";} else if ((bytes >= kilobyte) && (bytes < megabyte)) {return (bytes / kilobyte) + " KB";} else if ((bytes >= megabyte) && (bytes < gigabyte)) {return (bytes / megabyte) + " MB";} else if ((bytes >= gigabyte) && (bytes < terabyte)) {return (bytes / gigabyte) + " GB";} else if (bytes >= terabyte) {return (bytes / terabyte) + " TB";} else {return bytes + " Bytes";}
}

文章翻译自Stack Overflow：https://stackoverflow.com/questions/3758606/how-can-i-convert-byte-size-into-a-human-readable-format-in-java