# Java 程序：將二進制數轉換為十進制，反之亦然 > 原文： [https://www.programiz.com/java-programming/examples/binary-decimal-convert](https://www.programiz.com/java-programming/examples/binary-decimal-convert) #### 在此程序中，您將學習使用 Java 中的函數將二進制數轉換為十進制數，反之亦然。 訪問此頁面以了解[如何將二進制數轉換為十進制](http://www.wikihow.com/Convert-from-Binary-to-Decimal "Binary number to Decimal")。 ## 示例 1：將二進制數轉換為十進制的程序 ```java public class BinaryDecimal { public static void main(String[] args) { long num = 110110111; int decimal = convertBinaryToDecimal(num); System.out.printf("%d in binary = %d in decimal", num, decimal); } public static int convertBinaryToDecimal(long num) { int decimalNumber = 0, i = 0; long remainder; while (num != 0) { remainder = num % 10; num /= 10; decimalNumber += remainder * Math.pow(2, i); ++i; } return decimalNumber; } } ``` 運行該程序時，輸出為： ```java 110110111 in binary = 439 in decimal ``` * * * 訪問此頁面以了解[如何將十進制數轉換為二進制](http://www.wikihow.com/Convert-from-Decimal-to-Binary "Binary number to Decimal")。 ## 示例 2：將十進制數轉換為二進制的程序 ```java public class DecimalBinary { public static void main(String[] args) { int num = 19; long binary = convertDecimalToBinary(num); System.out.printf("%d in decimal = %d in binary", num, binary); } public static long convertDecimalToBinary(int n) { long binaryNumber = 0; int remainder, i = 1, step = 1; while (n!=0) { remainder = n % 2; System.out.printf("Step %d: %d/2, Remainder = %d, Quotient = %d\n", step++, n, remainder, n/2); n /= 2; binaryNumber += remainder * i; i *= 10; } return binaryNumber; } } ``` 運行該程序時，輸出為： ```java Step 1: 19/2, Remainder = 1, Quotient = 9 Step 2: 9/2, Remainder = 1, Quotient = 4 Step 3: 4/2, Remainder = 0, Quotient = 2 Step 4: 2/2, Remainder = 0, Quotient = 1 Step 5: 1/2, Remainder = 1, Quotient = 0 19 in decimal = 10011 in binary ```