In the previous article, we have discussed Java Program for Binary to Hexadecimal

In this article we will discuss about how to convert Octal to Decimal.

## Program To Convert Octal To Decimal

Before jumping into the program directly, let’s first know about octal and decimal.

**Decimal Number : **

- The number system with base 10 is generally called decimal number system .
- This number system us usually consists of 10 digits i.e. 0,1,2,3,4,5,6,7,8,9
- This is the popular number system which is used in daily life .
- Example – (156)
_{10 }where “10” represents the base and “156” represents the decimal number.

**Octal Number : **

- The number system with base 8 is generally called octal number system .
- This number system us usually consists of 8 digits i.e. 0,1,2,3,4,5,6,7
- Example – (156)
_{8 }where “8” represents the base and “156” represents the octal - But (186)
_{8 }will be a wrong representation because the digits are possible between 0 to 7

Now while converting to the octal to decimal

As the base is 8 so We need to multiply the digits with the base value with the power of 8 .

For example : lets take a octal number system (55)_{8 } we need to convert with the equivalent decimal value . so ,

(55)_{8 } = (5 × 8¹) + (5 × 8⁰)

= 40+5

= 45

Which can be represented as (45)_{10}

Let’s see different ways to convert Octal to Decimal.

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### Method 1 : Java Program for Octal to Decimal Using Integer.parseInt() method

**Approach :**

- Take a octal value form the input .
- Convert it into its decimal value by using
`Integer.parseInt(input value , 8)`

; - Store it into a variable .
- Print the result .

**Program :**

Let’s see the program to understand it more clearly.

import java.util.Scanner; public class Main { public static void main(String[] args) { // creating scanner object Scanner sc = new Scanner(System.in); // input an octal value as a string through scanner class System.out.println("Enter a octal Value : "); String input1=sc.next(); // converting to decimal int output =Integer.parseInt(input1, 8); System.out.println("Converted integer is : "+output); } }

Output : Enter an octal Value : 55 Converted integer is :45

### Method 2 : Java Program for Octal to Decimal By using mathematical approach

**Approach :**

- Take a octal value form the input .
- Take a for loop to iterate each digits of octal value and multiply with the power of 8 according to there position .
- Each time store it into a intermediate variable .
- After successful termination of loop Print the result .

**Program :**

Let’s see the program to understand it more clearly.

import java.util.Scanner; public class Main { public static void main(String[] args) { // creating scanner object Scanner sc = new Scanner(System.in); // input an octal value as a string through scanner class System.out.println("Enter a octal Value : "); int input1=sc.nextInt(); int x = input1; int output=0; // converting to Integer for (int a = 0; x > 0; a++) { // Taking the last digit int temp = x % 10; // power on 8 suitable to its position. double p = Math.pow(8, a); // Multiplying the digits to the Input and then adding it to result output += (temp * p); x = x / 10; } System.out.println("Converted integer is :"+output); } }

Output : Enter an octal Value : 55 Converted integer is :45

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