这是另一个简洁的解决方案，没有循环，但具有区域敏感格式和正确的二进制前缀:

import java.util.Locale;

public final class Bytes {

  private Bytes() {
  }

  public static String format(long value, Locale locale) {
    if (value < 1024) {
      return value + " B";
    }
    int z = (63 - Long.numberOfLeadingZeros(value)) / 10;
    return String.format(locale, "%.1f %siB", (double) value / (1L << (z * 10)), " KMGTPE".charAt(z));
  }
}

测试:

Locale locale = Locale.getDefault()
System.out.println(Bytes.format(1L, locale))
System.out.println(Bytes.format(2L * 1024, locale))
System.out.println(Bytes.format(3L * 1024 * 1024, locale))
System.out.println(Bytes.format(4L * 1024 * 1024 * 1024, locale))
System.out.println(Bytes.format(5L * 1024 * 1024 * 1024 * 1024, locale))
System.out.println(Bytes.format(6L * 1024 * 1024 * 1024 * 1024 * 1024, locale))
System.out.println(Bytes.format(Long.MAX_VALUE, locale))

输出:

1 B
2.0 KiB
3.0 MiB
4.0 GiB
5.0 GiB
6.0 PiB
8.0 EiB

filename=filedilg.getSelectedFile().getAbsolutePath();
File file=new File(filename);

String disp=FileUtils.byteCountToDisplaySize(file.length());
System.out.println("THE FILE PATH IS "+file+"THIS File SIZE IS IN MB "+disp);

String[] fileSizeUnits = {"bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"};

public String calculateProperFileSize(double bytes){
    String sizeToReturn = "";
    int index = 0;
    for(index = 0; index < fileSizeUnits.length; index++){
        if(bytes < 1024){
            break;
        }
        bytes = bytes / 1024;
    }

    System.out.println("File size in proper format: " + bytes + " " + fileSizeUnits[index]);
    sizeToReturn = String.valueOf(bytes) + " " + fileSizeUnits[index];
    return sizeToReturn;
}

只需添加更多的文件单元(如果有任何缺失)，你将看到单元大小达到该单元(如果你的文件有那么长):

我通常是这样做的:

public static String getFileSize(double size) {
    return _getFileSize(size,0,1024);
}

public static String _getFileSize(double size, int i, double base) {
    String units = " KMGTP";
    String unit = (i>0)?(""+units.charAt(i)).toUpperCase()+"i":"";
    if(size<base)
        return size +" "+unit.trim()+"B";
    else {
        size = Math.floor(size/base);
        return _getFileSize(size,++i,base);
    }
}

我们可以完全避免使用缓慢的Math.pow()和Math.log()方法，而不会牺牲简单性，因为单位之间的因子(例如，B, KB, MB等)是1024，即2^10。Long类有一个方便的numberofleadingzero()方法，我们可以用它来告诉大小值落在哪个单元中。

重点:大小单位的距离为10位(1024 = 2^10)，这意味着最高位的位置-换句话说，前导零的数量-相差10(字节= KB*1024, KB = MB*1024，等等)。

前导零数与大小单位的相关性:

最终代码:

public static String formatSize(long v) {
    if (v < 1024) return v + " B";
    int z = (63 - Long.numberOfLeadingZeros(v)) / 10;
    return String.format("%.1f %sB", (double)v / (1L << (z*10)), " KMGTPE".charAt(z));
}

private static final String[] Q = new String[]{"", "K", "M", "G", "T", "P", "E"};

public String getAsString(long bytes)
{
    for (int i = 6; i > 0; i--)
    {
        double step = Math.pow(1024, i);
        if (bytes > step) return String.format("%3.1f %s", bytes / step, Q[i]);
    }
    return Long.toString(bytes);
}