Problem: Write a Java program to convert a decimal number into its corresponding octal representation.
Example:
1 2 3 4 5 | Input: 7 Output: 7 Input: 8 Output: 10 |
Method 1: Using While Loop
To convert a decimal into octal we divide the decimal number by 8 until it reduces to 0 and stacks the sequence of remainders in a bottom-up manner.
In the Java program, we divide and concatenate remainders inside a while loop as follows:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | import java.util.Scanner; public class Main { public static void main(String[] args) { Scanner in = new Scanner(System.in); int octal=0, i=1, remainder; //Input the decimal number System.out.println("Enter a Decimal Number"); int decimal = in.nextInt(); //loop until the decimal is not 0 while(decimal>0){ remainder = decimal%8; //compute remainder octal += i*remainder; //concatenate remainders to the octal decimal = decimal/8; //update decimal with quotient i=i*10; //multiply 10 to i } //output the octal number System.out.println("Octal: "+octal); } } |
Output:
Enter a Decimal Number
15
Octal: 17
To concatenate remainders in a bottom-up manner, we first multiply the remainder with 10number_of_digits_in_octal (i*10) then add it to the octal number.
Method 2: Using Recursion
We can also convert a decimal number into an octal number using the recursive approach.
To do so, we recursively call the function with the quotient value (decimal/8) and print the remainder after the recursive call.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | import java.util.Scanner; public class Main { public static void main(String[] args) { Scanner in = new Scanner(System.in); //Input the decimal number System.out.println("Enter a Decimal Number"); int decimal = in.nextInt(); System.out.print("Octal: "); decToOctal(decimal); //call the recursive function } private static void decToOctal(int n){ if(n>0){ //recall by passing quotient decToOctal(n/8); //output the remainder System.out.print(n%8); } } } |
Output:
Enter a Decimal Number
8
Octal: 10
By writing the print statement after the recursive call statement, the remainders gets printed in the bottom-up sequence.
It is so because the print action starts when the recursive function starts tracing back to its first recursive call.