http://snippets.dzone.com/posts Thu, 21 Aug 2008 14:04:11 GMT DZone Snippets: conversion code http://snippets.dzone.com/posts/show/4594 Handy to store large numbers in a shorter notation. Doesn't work with negative numbers (for negative numbers you need to store an additional byte to indicate a positive or negative value, pass the absolute value). <br /> <br /><code> <br /> private static final short BASE_40_RADIX = 40; <br /> private static final short BASE_40_BASE = 48; <br /> private static final String BASE_40_ZERO = "0"; <br /> <br /> public static long fromBase40(char[] cs) { <br /> return fromBase(cs, BASE_40_BASE, BASE_40_RADIX); <br /> } <br /> <br /> public static char[] toBase40(final long i) { <br /> return toBase(i, BASE_40_BASE, BASE_40_RADIX, BASE_40_ZERO); <br /> } <br /> <br /> private static final short BASE_75_RADIX = 75; <br /> private static final short BASE_75_BASE = 48; <br /> private static final String BASE_75_ZERO = "0"; <br /> <br /> public static long fromBase75(char[] cs) { <br /> return fromBase(cs, BASE_75_BASE, BASE_75_RADIX); <br /> } <br /> <br /> public static char[] toBase75(final long i) { <br /> return toBase(i, BASE_75_BASE, BASE_75_RADIX, BASE_75_ZERO); <br /> } <br /> <br /> private static final short BASE_90_RADIX = 90; <br /> private static final short BASE_90_BASE = 33; <br /> private static final String BASE_90_ZERO = "!"; <br /> <br /> public static long fromBase90(char[] cs) { <br /> return fromBase(cs, BASE_90_BASE, BASE_90_RADIX); <br /> } <br /> <br /> public static char[] toBase90(final long i) { <br /> return toBase(i, BASE_90_BASE, BASE_90_RADIX, BASE_90_ZERO); <br /> } <br /> <br /> private static char[] toBase(final long i, final short base, final short radix, String nullCharacter) { <br /> long value = i; <br /> <br /> if (value == 0) { <br /> return nullCharacter.toCharArray(); <br /> } <br /> <br /> String result = ""; <br /> while (value > 0) { <br /> long mod = value % radix; <br /> value -= mod; <br /> if (value > 0) value /= radix; <br /> result = (char)(mod + base) + result; <br /> } <br /> <br /> return result.toCharArray(); <br /> } <br /> <br /> private static long fromBase(char[] cs, final short base, final short radix) { <br /> long value = 0; <br /> for (int i = cs.length - 1; i >= 0; i--) { <br /> int digit = ((int)cs[i]) - base; <br /> if (digit < 0 || digit >= radix) { <br /> throw new IllegalArgumentException("Invalid Base" + radix + " character: " + cs[i]); <br /> } <br /> long digitBase = (long)Math.pow(radix, (cs.length - 1) - i); <br /> value = (digit * digitBase) + value; <br /> } <br /> <br /> return value; <br /> } <br /></code> <br /> <br />And here are some tests: <br /> <br /><code> <br /> public void testFromBase40() { <br /> assertEquals(2559999, NumberUtils.fromBase40("WWWW".toCharArray())); <br /> assertEquals(1117580, NumberUtils.fromBase40("ABCD".toCharArray())); <br /> <br /> assertEquals(0, NumberUtils.fromBase40("0".toCharArray())); <br /> assertEquals(1, NumberUtils.fromBase40("1".toCharArray())); <br /> <br /> assertEquals(40, NumberUtils.fromBase40("10".toCharArray())); <br /> assertEquals(80, NumberUtils.fromBase40("20".toCharArray())); <br /> <br /> assertEquals(41, NumberUtils.fromBase40("11".toCharArray())); <br /> assertEquals(81, NumberUtils.fromBase40("21".toCharArray())); <br /> <br /> assertEquals(81, NumberUtils.fromBase40("0021".toCharArray())); <br /> <br /> assertEquals(3061560805L, NumberUtils.fromBase40("MSTSD5".toCharArray())); <br /> } <br /> <br /> public void testToBase40() { <br /> assertEquals("0", new String(NumberUtils.toBase40(0))); <br /> assertEquals("1", new String(NumberUtils.toBase40(1))); <br /> <br /> assertEquals("10", new String(NumberUtils.toBase40(40))); <br /> assertEquals("20", new String(NumberUtils.toBase40(80))); <br /> <br /> assertEquals("11", new String(NumberUtils.toBase40(41))); <br /> assertEquals("21", new String(NumberUtils.toBase40(81))); <br /> <br /> assertEquals("ABCD", new String(NumberUtils.toBase40(1117580))); <br /> assertEquals("WWWW", new String(NumberUtils.toBase40(2559999))); <br /> <br /> assertEquals("MSTSD5", new String(NumberUtils.toBase40(3061560805L))); <br /> <br /> } <br /> <br /> public void testToBase90() throws Exception { <br /> assertEquals("#Q&Y.`QY#", new String(NumberUtils.toBase90(10908158098650842L))); <br /> } <br /> <br /> public void testFromBase90() throws Exception { <br /> assertEquals(10908158098650842L, NumberUtils.fromBase90("#Q&Y.`QY#".toCharArray())); <br /> } <br /></code> <br /> Sun, 30 Sep 2007 23:44:48 GMT http://snippets.dzone.com/posts/show/4594 devijvers (Steven Devijver)