# Java: Convert a binary number to a Octal number

## Java Basic: Exercise-24 with Solution

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

Binary number: A binary number is a number expressed in the base-2 numeral system or binary numeral system. This system uses only two symbols: typically 0(zero) and 1(one).

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

*Test Data:*

Input a binary number: 111

**Pictorial Presentation: Binary to Octal number**

**Sample Solution:**

**Java Code:**

```
import java.util.*;
public class Exercise24 {
public static void main(String[] args) {
// Declare variables to store binary and decimal numbers, remainder, quotient, and an array for octal digits
int binnum, binnum1, rem, decnum = 0, quot, i = 1, j;
int octnum[] = 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 binary number
System.out.print("Input a Binary Number : ");
binnum = scan.nextInt();
binnum1 = binnum;
// Convert the binary number to decimal
while (binnum > 0) {
rem = binnum % 10;
decnum = decnum + rem * i;
i = i * 2;
binnum = binnum / 10;
}
i = 1;
quot = decnum;
// Convert the decimal number to octal
while (quot > 0) {
octnum[i++] = quot % 8;
quot = quot / 8;
}
// Display the equivalent octal value of the original binary number
System.out.print("Equivalent Octal Value of " + binnum1 + " is :");
for (j = i - 1; j > 0; j--) {
System.out.print(octnum[j]);
}
System.out.print("\n");
}
}
```

**Explanation:**

In the exercise above -

- First, initialize an array 'octnum' to store the octal digits of the converted number and other necessary variables.
- It takes a binary number as input from the user using the "Scanner" class and stores it in the variable 'binnum'.
- Next it enters a loop to convert the binary number to decimal:
- In each iteration, it calculates the remainder when 'binnum' is divided by 10 (which gives the least significant binary digit).
- It adds this remainder multiplied by i to the 'decnum' variable to accumulate the decimal value.
- It multiplies 'i' by 2 to prepare for the next binary digit.
- It updates 'binnum' by removing the least significant digit (rightmost) and by dividing it by 10.
- The loop continues until 'binnum' becomes zero, effectively converting the entire binary number to decimal.
- After converting to decimal, it enters another loop to convert the decimal number to octal:
- In each iteration, it calculates the remainder when 'decnum' is divided by 8 (which gives the least significant octal digit).
- It stores this remainder in the 'octnum' array.
- It updates 'decnum' by dividing it by 8 to move to the next octal digit.
- Finally, it prints the octal representation of the original binary number by iterating through the 'octnum' array in reverse order.

Sample Output:

Enter Binary Number : 111 Equivalent Octal Value of 111 is :7

**Flowchart: **

**Java Code Editor:**

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

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

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