java 自定义进制

1、10进制转其它进制( a 代表 10进制值)

10进制转2进制： Integer.toBinaryString(a);

10进制转8进制： Integer.toOctalString(a);

10进制转16进制：Integer.toHexString(a);

10进制转n进制：Integer.toString(a, n);

源码参考理解，Integer.class

public static String toString(int i, int radix) {

if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)

radix = 10;

/* Use the faster version */

if (radix == 10) {

return toString(i);

}

char buf[] = new char[33];

boolean negative = (i < 0);

int charPos = 32;

if (!negative) {

i = -i;

}

while (i

throw new NumberFormatException("radix " + radix +

" greater than Character.MAX_RADIX");

}

int result = 0;

boolean negative = false;

int i = 0, len = s.length();

int limit = -Integer.MAX_VALUE; // MAX_VALUE = 0x7fffffff

int multmin;

int digit;

if (len > 0) {

char firstChar = s.charAt(0);

if (firstChar < '0') { // Possible leading "+" or "-"

if (firstChar == '-') {

negative = true;

limit = Integer.MIN_VALUE; // MIN_VALUE = 0x80000000

} else if (firstChar != '+')

throw NumberFormatException.forInputString(s);

if (len == 1) // Cannot have lone "+" or "-"

throw NumberFormatException.forInputString(s);

i++;

}

multmin = limit / radix;

while (i < len) {

// Accumulating negatively avoids surprises near MAX_VALUE

digit = Character.digit(s.charAt(i++),radix);

if (digit < 0) {

throw NumberFormatException.forInputString(s);

}

if (result < multmin) {

throw NumberFormatException.forInputString(s);

}

result *= radix;

if (result < limit + digit) {

throw NumberFormatException.forInputString(s);

}

result -= digit;

}

} else {

throw NumberFormatException.forInputString(s);

}

return negative ? result : -result;

}