Convert decimal to octal in Java

In this post, you will learn how to convert decimal to octal using Java programming.

A decimal number is a base-10 number system where the range of numbers is 0,1,2,3,4,5,6,7,8,9. The main advantages of Decimal Number System are easy-to-read, used by humans and easy to manipulate. But there are some disadvantages, like wastage of space and time.

The octal number system has a base of eight like 23₈, 102₈, 41₈, etc. and uses the number from 0 to 7. The octal number system is widely used in computer application sectors and digital numbering systems. The main advantage of using Octal numbers is that it uses less digits than decimal and Hexadecimal number system. That's why it has fewer computations and less computational errors.

Java program to convert decimal to octal using Integer.toOctalString()

Java provides a built-in Integer.toOctalString() function to convert various values to a octal number. This function returns octal value.

// Java program to convert decimal to octal

public class DecimalToOctalExample1{  
    public static void main(String args[]){  

        // convert decimal value into octal  
        System.out.println("Octal value of 18 : "+Integer.toOctalString(18));  
        System.out.println("Octal value of 4 : "+Integer.toOctalString(4));  
        System.out.println("Octal value of 15 : "+Integer.toOctalString(15));  
        System.out.println("Octal value of 12 : "+Integer.toOctalString(12));  
        System.out.println("Octal value of 91 : "+Integer.toOctalString(91)); 
    }
}  

Octal value of 18 : 22
Octal value of 4 : 4
Octal value of 15 : 17
Octal value of 12 : 14
Octal value of 91 : 133

Java program to convert decimal to octal using while loop

Here, we have applied custom logic to convert decimal to octal in Java.

// Java program to convert decimal to octal
public class ConvertDecimalToOctal{    
        
    // creating function for conversion 
    public static String decimalToOctal(int decimal){    
        
        //declaring variable to store remainder  
        int rem;
        
        //declaring variable to store octal  
        String octal=""; 
        
        // declaring array of octal numbers  
        char octalchars[]={'0','1','2','3','4','5','6','7'};  
        
        // logic for decimal to octal conversion   
        while(decimal>0)  
        {  
           // Calculating remainder    
           rem=decimal%8;   
           
           // storing the octal value
           octal=octalchars[rem]+octal;   
           decimal=decimal/8;  
        }  
        return octal;  
    }    
    public static void main(String args[]){      
        
        // Calling function to get the octal number of given decimal value  
        System.out.println("Decimal to octal of 8 is: "+decimalToOctal(8));  
        System.out.println("Decimal to octal of 19 is: "+decimalToOctal(19));  
        System.out.println("Decimal to octal of 81 is: "+decimalToOctal(81));  
        System.out.println("Decimal to octal of 23 is: "+decimalToOctal(23));  
        System.out.println("Decimal to octal of 91 is: "+decimalToOctal(91));          
    }
} 

Decimal to octal of 8 is: 10
Decimal to octal of 19 is: 23
Decimal to octal of 81 is: 121
Decimal to octal of 23 is: 27
Decimal to octal of 91 is: 133

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