Why Does Java Interpret Integer Literals with Leading Zeroes as Octal?

Interpreting Integer Literals with Leading Zeroes

In Java, integer literals with leading zeroes are interpreted as octal (base-8) numbers. This behavior can be puzzling, especially when compared to decimal (base-10) literals.

Consider the following code:

System.out.println(0123); // Prints 83
System.out.println(123); // Prints 123

Explanation:

• 0123 begins with a leading zero, indicating an octal literal. To convert from octal to decimal, multiply each digit by the corresponding power of 8 and sum the results:

(1 * 8 * 8) + (2 * 8) + (3) = 83

Therefore, 0123 is interpreted as 83 in decimal.

• 123 has no leading zero, so it is interpreted as a decimal literal, resulting in the expected value of 123.

Avoiding Octal Interpretation:

To avoid unexpected octal interpretations, simply omit the leading zero from integer literals that are not intended to represent octal numbers.

Hexadecimal Literals:

Java also supports hexadecimal (base-16) literals, which are prefixed with 0x. For example:

System.out.println(0x123); // Prints 291

In this case, 0x123 represents the hexadecimal value 123, which is equivalent to 291 in decimal.

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