# Java: Convert a decimal number to octal number

## Java Basic: Exercise-21 with Solution

Write a Java program to convert a decimal number to an octal number.

Decimal number: The decimal numeral system is the standard system for denoting integer and non-integer numbers. It is also called base-ten positional numeral system.

Octal number: The octal numeral system is the base-8 number system, and uses the digits 0 to 7.

**Pictorial Presentation: Decimal to Octal number**

**Sample Solution:**

**Java Code:**

```
import java.util.Scanner;
public class Exercise21 {
public static void main(String args[]) {
// Declare variables to store decimal number, remainder, quotient, and an array for octal digits
int dec_num, rem, quot, i = 1, j;
int oct_num[] = new int[100];
// Create a Scanner object to read input from the user
Scanner scan = new Scanner(System.in);
// Prompt the user to input a decimal number
System.out.print("Input a Decimal Number: ");
dec_num = scan.nextInt();
// Initialize the quotient with the decimal number
quot = dec_num;
// Convert the decimal number to octal and store octal digits
while (quot != 0) {
oct_num[i++] = quot % 8;
quot = quot / 8;
}
// Display the octal representation of the decimal number
System.out.print("Octal number is: ");
for (j = i - 1; j > 0; j--) {
System.out.print(oct_num[j]);
}
System.out.print("\n");
}
}
```

**Explanation:**

In the exercise above -

- It takes a decimal number ('dec_num') as input from the user using the "Scanner" class.
- It initializes an array 'oct_num' to store the octal digits of the converted number and other necessary variables.
- It enters a loop to perform the decimal-to-octal conversion:
- In each iteration, it calculates the remainder of 'dec_num' when divided by 8 and stores it in the 'oct_num' array.
- It then updates 'dec_num' by dividing it by 8 (which effectively shifts it to the right).
- The loop continues until 'dec_num' becomes zero, effectively converting the entire decimal number to octal.
- After the loop, it prints the octal representation of the decimal number by iterating through the 'oct_num' array in reverse order.

Sample Output:

Input a Decimal Number: 15 Octal number is: 17

**Flowchart: **

**Java Code Editor:**

**Previous:** Write a Java program to convert a decimal number to hexadecimal number.

**Next:** Write a Java program to convert a binary number to decimal number.

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