Java - Convert Human Readable Size to Bytes

问题:

I've found lots of information about converting raw byte information into a human-readable format, but I need to do the opposite, i.e. convert the String "1.6 GB" into the long value 1717990000. Is there an in-built/well-defined way to do this, or will I pretty much have to roll my own?

[Edit]: Here is my first stab...

static class ByteFormat extends NumberFormat {     @Override     public StringBuffer format(double arg0, StringBuffer arg1, FieldPosition arg2) {         // TODO Auto-generated method stub         return null;     }      @Override     public StringBuffer format(long arg0, StringBuffer arg1, FieldPosition arg2) {         // TODO Auto-generated method stub         return null;     }      @Override     public Number parse(String arg0, ParsePosition arg1) {         return parse (arg0);     }      @Override     public Number parse(String arg0) {         int spaceNdx = arg0.indexOf(" ");         double ret = Double.parseDouble(arg0.substring(0, spaceNdx));         String unit = arg0.substring(spaceNdx + 1);         int factor = 0;         if (unit.equals("GB")) {             factor = 1073741824;         }         else if (unit.equals("MB")) {             factor = 1048576;         }         else if (unit.equals("KB")) {             factor = 1024;         }          return ret * factor;     } }

回答1:

I've never heard about such well-known library, which implements such text-parsing utility methods. But your solution seems to be near from correct implementation.

The only two things, which I'd like to correct in your code are:

1. define method Number parse(String arg0) as static due to it utility nature

2. define factors for each type of size definition as final static fields.

I.e. it will be like this one:

private final static long KB_FACTOR = 1024; private final static long MB_FACTOR = 1024 * KB_FACTOR; private final static long GB_FACTOR = 1024 * MB_FACTOR;  public static double parse(String arg0) {     int spaceNdx = arg0.indexOf(" ");     double ret = Double.parseDouble(arg0.substring(0, spaceNdx));     switch (arg0.substring(spaceNdx + 1)) {         case "GB":             return ret * GB_FACTOR;         case "MB":             return ret * MB_FACTOR;         case "KB":             return ret * KB_FACTOR;     }     return -1; }

回答2:

A revised version of Andremoniy's answer that properly distinguishes between kilo and kibi, etc.

private final static long KB_FACTOR = 1000; private final static long KIB_FACTOR = 1024; private final static long MB_FACTOR = 1000 * KB_FACTOR; private final