# Java 程序：將二進制數轉換為八進制，反之亦然 > 原文： [https://www.programiz.com/java-programming/examples/binary-octal-convert](https://www.programiz.com/java-programming/examples/binary-octal-convert) #### 在此程序中，您將學習如何使用 Java 中的函數將二進制數轉換為八進制數，反之亦然。 ## 示例 1：將二進制轉換為八進制的程序 在此程序中，我們將首先將二進制數轉換為十進制。 然后，十進制數字轉換為八進制。 ```java public class BinaryOctal { public static void main(String[] args) { long binary = 101001; int octal = convertBinarytoOctal(binary); System.out.printf("%d in binary = %d in octal", binary, octal); } public static int convertBinarytoOctal(long binaryNumber) { int octalNumber = 0, decimalNumber = 0, i = 0; while(binaryNumber != 0) { decimalNumber += (binaryNumber % 10) * Math.pow(2, i); ++i; binaryNumber /= 10; } i = 1; while (decimalNumber != 0) { octalNumber += (decimalNumber % 8) * i; decimalNumber /= 8; i *= 10; } return octalNumber; } } ``` 運行該程序時，輸出為： ```java 101001 in binary = 51 in octal ``` 此轉換發生為： ```java Binary To Decimal 1 * 25 + 0 * 24 + 1 * 23 + 0 * 22 + 0 * 21 + 1 * 20 = 41 Decimal to Octal 8 | 41 8 |5 -- 1 8 |0 -- 5 (51) ``` * * * ## 示例 2：將八進制轉換為二進制的程序 在此程序中，八進制數首先從十進制到十進制。 然后，將十進制數轉換為二進制數。 ```java public class OctalBinary { public static void main(String[] args) { int octal = 67; long binary = convertOctalToBinary(octal); System.out.printf("%d in octal = %d in binary", octal, binary); } public static long convertOctalToBinary(int octalNumber) { int decimalNumber = 0, i = 0; long binaryNumber = 0; while(octalNumber != 0) { decimalNumber += (octalNumber % 10) * Math.pow(8, i); ++i; octalNumber/=10; } i = 1; while (decimalNumber != 0) { binaryNumber += (decimalNumber % 2) * i; decimalNumber /= 2; i *= 10; } return binaryNumber; } } ``` 運行該程序時，輸出為： ```java 67 in octal = 110111 in binary ``` This conversion takes place as: ```java Octal To Decimal 6 * 81 + 7 * 80 = 55 Decimal to Binary 2 | 55 2 | 27 -- 1 2 | 13 -- 1 2 | 6 -- 1 2 | 3 -- 0 2 | 1 -- 1 2 |0 -- 1 (110111) ```