文件大小工具类.

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/** * <p> * 文件大小工具类. * </p> * * @author poplar.yfyang * @version 1.0 2013-01-02 12:50 PM * @since JDK 1.5 */public class FileSizeHelper {    public static long ONE_KB = 1024;    public static long ONE_MB = ONE_KB * 1024;    public static long ONE_GB = ONE_MB * 1024;    public static long ONE_TB = ONE_GB * (long)1024;    public static long ONE_PB = ONE_TB * (long)1024;    public static String getHumanReadableFileSize(Long fileSize) {        if(fileSize == null) return null;        return getHumanReadableFileSize(fileSize.longValue());    }    public static String getHumanReadableFileSize(long fileSize) {        if(fileSize < 0) {            return String.valueOf(fileSize);        }        String result = getHumanReadableFileSize(fileSize, ONE_PB, "PB");        if(result != null) {            return result;        }        result = getHumanReadableFileSize(fileSize, ONE_TB, "TB");        if(result != null) {            return result;        }        result = getHumanReadableFileSize(fileSize, ONE_GB, "GB");        if(result != null) {            return result;        }        result = getHumanReadableFileSize(fileSize, ONE_MB, "MB");        if(result != null) {            return result;        }        result = getHumanReadableFileSize(fileSize, ONE_KB, "KB");        if(result != null) {            return result;        }        return String.valueOf(fileSize)+"B";    }    private static String getHumanReadableFileSize(long fileSize, long unit, String unitName) {        if(fileSize == 0) return "0";        if(fileSize / unit >= 1) {            double value = fileSize / (double)unit;            DecimalFormat df = new DecimalFormat("######.##"+unitName);            return df.format(value);        }        return null;    }}
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