现在，我正在尝试找到一种方法，在Java中将数字从一个基数转换为另一个基数，给出一个数字，数字所在的基数，以及转换为的基数。
public static void BaseConversion(String number, int base1, int base2){
//convert the number from one base to another
}
我找到了JavaScript的解决方案，我想知道是否有可能在Java中做类似的事情：
function convertFromBaseToBase(str, fromBase, toBase){
var num = parseInt(str, fromBase); //convert from one base to another
return num.toString(toBase);
}
答案 0 :(得分：50)
你可以做到
return Integer.toString(Integer.parseInt(number, base1), base2);
使用您的函数签名，在Java中：
public String convertFromBaseToBase(String str, int fromBase, int toBase) {
return Integer.toString(Integer.parseInt(str, fromBase), toBase);
}
答案 1 :(得分：8)
public class BaseToBaseConv {
static String baseToBase(String num, int base1, int base2) {
int no = convFrmBaseToDeci(num, base1);
return convFrmDecToBase(no, base2);
}
static String convFrmDecToBase(int num, int base) {
String res = "";
int rem;
// Convert input number is given base by repeatedly
// dividing it by base and taking remainder
while (num > 0) {
rem = num % base;
if (base == 16) {
if (rem == 10)
res += 'A';
else if (rem == 11)
res += 'B';
else if (rem == 12)
res += 'C';
else if (rem == 13)
res += 'D';
else if (rem == 14)
res += 'E';
else if (rem == 15)
res += 'F';
else
res += rem;
} else
res += rem;
num /= base;
}
// Reverse the result
return new StringBuffer(res).reverse().toString();
}
static int convFrmBaseToDeci(String num, int base) {
if (base < 2 || (base > 10 && base != 16))
return -1;
int val = 0;
int power = 1;
for (int i = num.length() - 1; i >= 0; i--) {
int digit = digitToVal(num.charAt(i));
if (digit < 0 || digit >= base)
return -1;
// Decimal equivalent is str[len-1]*1 +
// str[len-1]*base + str[len-1]*(base^2) + ...
val += digit * power;
power = power * base;
}
return val;
}
static int digitToVal(char c) {
if (c >= '0' && c <= '9')
return (int) c - '0';
else
return (int) c - 'A' + 10;
}
public static void main(String [] args) {
System.out.println(baseToBase("12345", 10, 2));
System.out.println(baseToBase("11000000111001", 2, 10));
System.out.println(baseToBase("ABC11", 16, 2));
System.out.println(baseToBase("10101011110000010001", 2, 16));
System.out.println(baseToBase("12322", 8, 16));
}
}
答案 2 :(得分：4)
我相信这会奏效：
long x = 10;
int baseToConvertTo = 9;
System.out.println(Long.toString(x, baseToConvertTo));
输出：11
答案 3 :(得分：3)
正如其他人所展示的那样，Integer.parseInt()可以为您做到这一点。但是，如果您自己尝试构建转换器，则以下操作只需将数值转换为所需的基数即可。注意，对于基数10以上的基数，你必须考虑alpha字符... I.E. 11-A，12-B等...
public class NumberUtil {
/**
* This example is convoluted as in reality it just uses 'toString' to convert the number...
* However, it displays the logic needed to make the conversion...
*
* To convert a number to a new radix, recursively return the remainder of the number
* divided by the radix for each operation until zero. Then return the concatenated value in reverse.
*
* Example convert 9658 to base 2
*
* 9658 / 2 = 4829 R 0
* 4829 / 2 = 2414 R 1
* 2414 / 2 = 1207 R 0
* 1207 / 2 = 603 R 1
* 603 / 2 = 301 R 1
* 301 / 2 = 150 R 1
* 150 / 2 = 75 R 0
* 75 / 2 = 37 R 1
* 37 / 2 = 18 R 1
* 18 / 2 = 9 R 0
* 9 / 2 = 4 R 1
* 4 / 2 = 2 R 0
* 2 / 2 = 1 R 0
* 1 / 2 = 0 R 1
*
* Answer :: 10010110111010
*
* @param number :: Integer number to convert.
* @param radix :: Radix to convert to.
* @return :: BigInteger of the number converted to the desired radix.
*/
static BigInteger convertBase( int number, int radix ) {
List<Integer> remainder = new ArrayList<>();
int count = 0;
String result = "";
while( number != 0 ) {
remainder.add( count, number % radix != 0 ? number % radix : 0 );
number /= radix;
try {
result += remainder.get( count );
} catch( NumberFormatException e ) {
e.printStackTrace();
}
}
return new BigInteger( new StringBuffer( result ).reverse().toString() );
}
public static void main( String[] args ) {
System.out.println( convertBase( 9658, 2 ) );
}
}
答案 4 :(得分：2)
测试：
class Test1 {
public static void main(String[] args) {
String s1 = "10";
int n1 = Integer.parseInt(s1, 8);
System.out.println(s1 + " is " + n1 + " in base10");
String s2 = Integer.toString(n1, 2);
System.out.println(n1 + " is " + s2 + " in base2");
}
}
给出：
C:\Temp>java Test1
10 is 8 in base10
8 is 1000 in base2
使用Integer.parseInt和Integer.toString。
答案 5 :(得分：1)
如果您可以确定相关数字分别在Integer.parseInt或Long.parseLong范围内，则int或long的双参数版本会执行此操作。如果您无法保证这一点，请使用java.math.BigInteger：
BigInteger bi = new BigInteger(number, base1);
return bi.toString(base2);
这可以处理任意大的整数，例如
System.out.println(
new BigInteger("12345678901234567890123456789", 10).toString(16));
// prints 27e41b3246bec9b16e398115 - too big to represent as a long
答案 6 :(得分：0)
由于您在js代码中提到int，因此Integer课程中有两种方法可供您查看：
static int parseInt(String s, int radix)
Parses the string argument as a signed integer in the radix specified by the second argument.
和
static String toString(int i, int radix)
Returns a string representation of the first argument in the radix specified by the second argument.
答案 7 :(得分：0)
使用此代码
import java.util.Scanner; // import scanner class
public class BaseConverting {
public static void main(String[] args) {
Scanner input = new Scanner(System.in); //creating object from Scanner class
String ans;
System.out.println("Enter the decimal value need to convert !");
int decimal_value = input.nextInt(); //getting decimal value from user
System.out.println("Select base \n Binary - b ;\n Octal- o ;\n HexaDecimal -h ;");
String choice = input.next(); //getting user needs Base type
switch (choice) {
case "b":
ans = Integer.toString(decimal_value, 2);
System.out.println("Binary value of " + decimal_value + " = " + ans);
break;
case "o":
ans = Integer.toString(decimal_value, 8);
System.out.println("Octal value of " + decimal_value + " = " + ans);
break;
case "h":
ans = Integer.toString(decimal_value, 16);
System.out.println("Hexa Decimal value of " + decimal_value + " = " + ans);
break;
}
}
}
答案 8 :(得分：0)
这个怎么样？
public static void main(String[] args) {
System.out.println(toDecimalBase("11111111", 2));
System.out.println(toDecimalBase("Ff", 16));
System.out.println(toDecimalBase("377", 8));
System.out.println(toDecimalBase("255", 10));
}
private static int toDecimalBase(String number, int base) {
int lenght = number.length();
int result = 0;
for (int i = 0; i < lenght; i++) {
// get char in a reverse order from the array
int character = number.charAt(lenght - i - 1);
// convert range [A-F] to range of [0-6]
if (character >= 'A' && character <= 'F') {
character = character - 'A' + 10;
}
else if (character >= 'a' && character <= 'f') {
character = character - 'a' + 10;
}
// Unicode to int
else {
character = Character.getNumericValue(character);
}
result += (Math.pow(base, i)) * character;
}
return result;
}
答案 9 :(得分：0)
BaseEncoder ：
BaseEncoder是为这个问题写的。
注释：
输出：
baseConversion("10011100", 2, 16) = "9C"
baseConversion("9c", 16, 2) = "10011100"
baseConversion("609643", 10, 64) = "2Krh"
baseConversion("33773377",10, 100) = "bÈbÈ"
baseConversion("18018018",10,1000) = "NNN"
使用：
sout("(\"10011100\", 2, 16)=" + baseConversion("10011100", 2, 16));
sout("(\"9c\", 16, 2)=" + baseConversion("9c", 16, 2));
sout("(\"609643\", 10, 64)=" + baseConversion("609643", 10, 64));
sout("(\"33773377\",10, 100)=" + baseConversion("33773377", 10, 100));
sout("(\"18018018\",10,1000)=" + baseConversion("18018018", 10, 1000));
来源：
/*
* Licensced for commercial or non-commercial use, modification and
* redistribution provided the source code retain this license header and
* attribution. Written to answer to Stack Overflow question 15735079. See
* https://stackoverflow.com/questions/15735079/
* to see the original questions and ( if this code has been modified ) to see
* the original source code. This license does not supercede any licencing
* requirements set forth by StackOverflow. In the event of a disagreement
* between this license and the terms of use set forth by StackOverflow, the
* terms of use and/or license set forth by StackOverflow shall be considered
* the governing terms and license.
*/
package org.myteam.util;
import java.math.BigInteger;
/**
* conversion routines to support
* <pre>
* BaseEncoder.baseConversion("94d6b", 16, 2));
* </pre> allowing conversions between numbering systems of base 2 to base 3263
* inclusive, with the following caveats:<ul>
* <li> WARNING: BASE64 numbers created or parsed with this encoder are not
* compatible with a standard base 64 encoder, and </li>
* <li> WARNING: this class does not currently support unicode, or if it does
* that's only by accident and it most likely does not support characters that
* require more than one codepoint.</li>
* </ul>
* . to convert between two non-standard numbering systems, use two BaseEncoder
* objects e.g.
* <pre>
*
* String numberBase64 = "1X3dt+4N";
* String numberBase16 = new BaseEncoder(16).fromBase10(new BaseEncoder(
* "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/")
* .toBase10(numberBase64));
*
* </pre>
*
* @see https://stackoverflow.com/questions/15735079/
*/
public class BaseEncoder {
public static void main(String[] args) {
sout("(\"10011100\", 2, 16)=" + baseConversion("10011100", 2, 16));
sout("(\"9c\", 16, 2)=" + baseConversion("9c", 16, 2));
sout("(\"609643\", 10, 64)=" + baseConversion("609643", 10, 64));
sout("(\"33773377\",10, 100)=" + baseConversion("33773377", 10, 100));
sout("(\"18018018\",10,1000)=" + baseConversion("18018018", 10, 1000));
// test();
}
private static void sout(String output) {
System.out.println("\tbaseConversion"
+ output.replace("=", " = \"") + "\"");
}
/**
* this is the method that satisfies the criteria set forth by the original
* question at https://stackoverflow.com/questions/15735079/ .
*
* @param fromNumber
* @param fromBase
* @param toBase
* @return
*/
public static String baseConversion(
String fromNumber, int fromBase, int toBase) {
final BigInteger numberBase10 = fromBase == 10
? new BigInteger(fromNumber)
: parseBigInteger(fromNumber, fromBase);
// System.out.println("org.myteam.util.baseConversion():"
// + " numberBase10 = " + numberBase10);
return toBase == 10 ? numberBase10.toString()
: toString(numberBase10, toBase);
}
/**
* Simple test to validate conversion functions. Should be converted to
* support whatever unit tests or automated test suite your organization
* employs. No return value.
*
* @throws IllegalStateException if any test fails, and aborts all tests.
*/
public static void test() throws IllegalStateException {
final int level1 = 100;
final int level2 = 525;
final int level3 = 1000;
final int maxlvl = 3263;
for (int radix = 2; radix < maxlvl;) {
test(radix);
radix += (radix < level1) ? 1
: (radix < level2) ? 17
: (radix < level3) ? 43
: 139;
}
test(3263);
System.out.println("taurus.BaseEncoder.test(): all tests passed.");
}
private static void test(int radix) throws IllegalStateException {
final BigInteger level1 = BigInteger.valueOf(radix);
final BigInteger level2 = level1.multiply(level1);
final BigInteger level3 = level2.multiply(level1);
final BigInteger maxlvl = level3.multiply(level1);
final BigInteger increment1 = BigInteger.ONE;
final BigInteger increment2 = level1.add(BigInteger.ONE);
final BigInteger increment3 = level2
.add(BigInteger.ONE).add(BigInteger.ONE).add(BigInteger.ONE);
final BigInteger increment4 = level3.add(BigInteger.valueOf(17));
final int exitLvl = 5;
int prevLvl = 1;
BigInteger iTest = BigInteger.ZERO;
while (true) {
Throwable err = null;
String radixEncoded = "(conversion to base " + radix + " failed)";
String backToBase10 = "(conversion back to base 10 failed)";
try {
radixEncoded = baseConversion("" + iTest, 10, radix);
backToBase10 = baseConversion(radixEncoded, radix, 10);
} catch (Throwable ex) {
err = ex;
}
if (err != null || !backToBase10.equals("" + iTest)) {
System.out.println("FAIL: "
+ iTest + " base " + radix + " = " + radixEncoded);
System.out.println("FAIL: "
+ radixEncoded + " base 10 = " + backToBase10
+ " (should be " + iTest + ")");
throw new IllegalStateException("Test failed. base 10 '" + iTest
+ "' conversion to/from base" + radix + ".", err);
}
int lvl = (prevLvl == 1 && iTest.compareTo(level1) >= 0) ? 2
: (prevLvl == 2 && iTest.compareTo(level2) >= 0) ? 3
: (prevLvl == 3 && iTest.compareTo(level3) >= 0) ? 4
: (prevLvl == 4 && iTest.compareTo(maxlvl) >= 0) ? exitLvl
: prevLvl;
final BigInteger increment
= (lvl == 1) ? increment1
: (lvl == 2) ? increment2
: (lvl == 3) ? increment3
: (lvl == 4) ? increment4
: BigInteger.ZERO;
iTest = iTest.add(increment);
if (prevLvl != lvl) {
if (lvl == exitLvl && (radix % 56 == 0 || radix > 2700)) {
System.out.println("test():" + " radix " + radix
+ " level " + prevLvl + " test passed.");
}
}
if (lvl == exitLvl) {
break;
}
prevLvl = lvl;
}
}
/**
* <pre>
* String tenAsOctal = toString(BigInteger.TEN, 8); // returns "12"
* </pre>.
*
* @param numberBase10
* @param radix
* @return
*/
public static String toString(BigInteger numberBase10, int radix) {
return new BaseEncoder(radix).fromBase10(numberBase10);
}
/**
* <pre>
* String tenAsOctal = toString(BigInteger.TEN, "01234567"); // returns "12"
* </pre>.
*
* @param numberBase10
* @param digits
* @return
*/
public static String toString(BigInteger numberBase10, String digits) {
return new BaseEncoder(digits).fromBase10(numberBase10);
}
/**
* <pre>
* String tenAsOctal = "12"; // ("1" x 8^1) + ("2" x 8^0) = 10
* String tenAsDecimal = parseBigInteger(tenAsOctal, 8);
* System.out.println(tenAsDecimal); // "10"
* </pre>.
*
* @param numberEncoded
* @param radix
* @return
*/
public static BigInteger parseBigInteger(String numberEncoded, int radix) {
return new BaseEncoder(radix).toBase10(numberEncoded);
}
/**
* <pre>
* String tenAsOctal = "12"; // ("1" x 8^1) + ("2" x 8^0) = 10
* String tenAsDecimal = parseBigInteger(tenAsOctal, "01234567");
* System.out.println(tenAsDecimal); // "10"
* </pre>.
*
* @param numberEncoded
* @param digits
* @return
*/
public static BigInteger parseBigInteger(
String numberEncoded, String digits) {
return new BaseEncoder(digits).toBase10(numberEncoded);
}
/**
* <pre>
* String tenAsOctal = "12"; // ("1" x 8^1) + ("2" x 8^0) = 10
* int tenAsDecimal = parseInt(tenAsOctal, 8);
* System.out.println(tenAsDecimal); // 10
* </pre>.
*
* @param numberEncoded
* @param radix
* @return
*/
public static int parseInt(String numberEncoded, int radix) {
return new BaseEncoder(radix).toBase10(numberEncoded).intValueExact();
}
/**
* <pre>
* String tenAsOctal = "12"; // ("1" x 8^1) + ("2" x 8^0) = 10
* int tenAsDecimal = parseInt(tenAsOctal, "01234567");
* System.out.println(tenAsDecimal); // 10
* </pre>.
*
* @param numberEncoded
* @param digits
* @return
*/
public static int parseInt(String numberEncoded, String digits) {
return new BaseEncoder(digits).toBase10(numberEncoded).intValueExact();
}
/**
* <pre>
* String tenAsOctal = "12"; // ("1" x 8^1) + ("2" x 8^0) = 10
* long tenAsDecimal = parseLong(tenAsOctal, 8);
* System.out.prlongln(tenAsDecimal); // 10
* </pre>.
*
* @param numberEncoded
* @param radix
* @return
*/
public static long parseLong(String numberEncoded, int radix) {
return new BaseEncoder(radix).toBase10(numberEncoded).longValueExact();
}
/**
* <pre>
* String tenAsOctal = "12"; // ("1" x 8^1) + ("2" x 8^0) = 10
* long tenAsDecimal = parseLong(tenAsOctal, "01234567");
* System.out.prlongln(tenAsDecimal); // 10
* </pre>.
*
* @param numberEncoded
* @param digits
* @return
*/
public static long parseLong(String numberEncoded, String digits) {
return new BaseEncoder(digits).toBase10(numberEncoded).longValueExact();
}
/**
* each character in this string represents one digit in the base-X
* numbering system supported by this instance, where X = the length of the
* string. e.g.
* <pre>
* base 2 (binary) digits = "01"
* base 8 (octal) digits = "01234567"
* base 10 (decimal) digits = "0123456789"
* base 16 (hexdecimal) digits = "0123456789ABCDEF"
* </pre> digits follow this pattern until base 64. a somewhat arbitrary
* character system is utilized to support base 65 to base 3263.
*/
private final String digits;
/**
* specify a numbering system between base 2 and base 64 inclusive
* <pre>
* String fiveAsBinary = new BaseEncoder(2).fromBase10(5);
* System.out.println(fiveAsBinary); // "101"
* </pre> to use a numbering system with more than 64 digits, or to use your
* own custom digits, use
* <pre>
* new BaseEncoder(String)
* </pre>.
*
* @param radix
*/
public BaseEncoder(int radix) {
String digitsTemp = getDefaultDigitsForBase(radix);
digits = digitsTemp;
}
/**
* specify digits to use for your numbering system for example base 16 could
* be represented as
* <pre>
* new BaseEncoder("0123456789ABCDEF")
* </pre> <br>
* and base 64 could be represented as
* <pre>
* new BaseEncoder("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
* + "abcdefgjijklmnopqrstuvwxyz+/")
* </pre>.
*
* @param digits
*/
public BaseEncoder(String digits) {
if (digits.length() < 2) {
final String errorMessage = "Supported bases include 2 and above."
+ " " + "Please provide at least two characters"
+ " " + "e.g. new BaseEncoder(\"01\") // binary or base 2";
throw new IllegalArgumentException(errorMessage);
}
this.digits = digits;
}
/**
* convert a number from a non-standard numbering format to base 10
* (BigInteger).
*
* @param numberEncoded
* @return
*/
public BigInteger toBase10(final String numberEncoded) {
final int radix = digits.length();
final BigInteger magnitude = BigInteger.valueOf(radix);
final char[] chars = numberEncoded.toCharArray();
BigInteger numberBase10 = BigInteger.ZERO;
for (int i = 0; i < chars.length; i++) {
numberBase10 = numberBase10.multiply(magnitude);
final char digitEncoded = chars[i];
final int indexOf = digits.indexOf(digitEncoded);
final int digitValue;
if (indexOf == -1) {
digitValue = digits.toLowerCase().indexOf(
Character.toLowerCase(digitEncoded));
} else {
digitValue = indexOf;
}
if (digitValue == -1) {
final String errorMessage = "Digit '" + digitEncoded + "'"
+ " " + "from base " + radix + " number"
+ " " + "'" + numberEncoded + "' not found in"
+ " " + "base " + radix + " digits '" + digits + "'.";
throw new IllegalArgumentException(errorMessage);
}
numberBase10 = numberBase10.add(BigInteger.valueOf(digitValue));
}
return numberBase10;
}
/**
* convert a number from a non-standard numbering format to base 10
* (BigInteger).
*
* @param numberBase10
* @return
*/
public String fromBase10(long numberBase10) {
return fromBase10(BigInteger.valueOf(numberBase10));
}
/**
* convert a number from a non-standard numbering format to base 10
* (BigInteger).
*
* @param numberBase10
* @return
*/
public String fromBase10(BigInteger numberBase10) {
final StringBuilder encodedNumber = new StringBuilder("");
final int radix = digits.length();
final BigInteger magnitude = BigInteger.valueOf(radix);
while (numberBase10.compareTo(BigInteger.ZERO) > 0) {
final BigInteger[] divideAndRemainder = numberBase10
.divideAndRemainder(magnitude);
final BigInteger quotient = divideAndRemainder[0];
final BigInteger remainder = divideAndRemainder[1];
encodedNumber.insert(0, digits.charAt(remainder.intValueExact()));
numberBase10 = quotient;
}
return encodedNumber.toString();
}
public static String getDefaultDigitsForBase(int radix) throws IllegalArgumentException {
if (radix < 2) {
final String errorMessage = "Supported bases include 2 and above."
+ " " + "Not really sure how to represent"
+ " " + "base " + radix + " numbers.";
throw new IllegalArgumentException(errorMessage);
} else if (radix <= 64) {
return ("0123456789ABCDEFGHIJKLMNOPQRSTUV" // base 32 ends at V
+ "WXYZabcdefghijklmnopqrstuvwxyz+/").substring(0, radix);
}
int charCount = 0;
final StringBuilder s = new StringBuilder();
for (int i = Character.MIN_VALUE; i < Character.MAX_VALUE; i++) {
switch (Character.getType(i)) {
case Character.CONNECTOR_PUNCTUATION:
case Character.CURRENCY_SYMBOL:
case Character.FINAL_QUOTE_PUNCTUATION:
case Character.INITIAL_QUOTE_PUNCTUATION:
case Character.LETTER_NUMBER:
case Character.LINE_SEPARATOR:
case Character.LOWERCASE_LETTER:
case Character.MATH_SYMBOL:
case Character.UPPERCASE_LETTER:
s.append((char) i);
if (++charCount >= radix) {
return s.toString();
}
break;
}
}
throw new IllegalArgumentException("Radix '" + radix + "' exceeds maximum '" + charCount + "'");
}
}