Understanding Octal Numbers in Java

The octal number system is a base-8 system, meaning it uses digits from 0 to 7. Digits 8 and 9 are not valid in octal representation. In Java, if an integer literal begins with a leading zero, it is interpreted as an octal number. Thus, the digits in such literals can only be between 0 and 7.

To denote an octal literal in Java code, prefix the number with a leading zero. For hexadecimal numbers, use the prefix 0x.

For example:

Octal Literal: 0757

Hexadecimal Literal: 0x1EF

Here’s an example demonstrating the different number systems and how they map to the same decimal value.

Explanation:

• Decimal: 255 is written directly as a base-10 number.
• Hexadecimal: 0xFF is a base-16 number.F in hexadecimal is 15, so 0xFF equals 15*16^1 + 15*16^0 = 255 in decimal.
• Octal: 0377 is a base-8 number. 0377 in base-8 is calculated as 3*8^2 + 7*8^1 + 7*8^0 = 192 + 56 + 7 = 255 in decimal.
• Binary: 0b11111111 is a base-2 number. 0b11111111 in base-2 is calculated as 1*2^7 + 1*2^6 + 1*2^5 + 1*2^4 + 1*2^3 + 1*2^2 + 1*2^1 + 1*2^0 = 128 + 64 + 32 + 16 + 8 + 4 + 2 + 1 = 255 in decimal.

When you run this code, all the output values will show 255, demonstrating that all these different representations are equivalent in their decimal form.

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To display an integer value in octal format, use the Integer.toOctalString(int) method. Conversely, to convert a string representing an octal number back into an integer, use Integer.parseInt(String value, int radix), specifying 8 as the radix.

Output :

Octal: 747
Parsed Octal: 495

Explanation:

1. Integer.toOctalString(decimal): Converts the decimal number 495 to its octal representation.495 in decimal is 747 in octal.
2. Integer.parseInt(octalString, 8): Converts the octal string 747 back to its decimal form.747 in octal converts back to 495 in decimal.

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