Question

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Integer with leading zeroes

Can someone please tell me what is going on here? When I initialize an int with leading zeroes the program does not ignore the zeroes and instead does some other operation I am unaware of.

int num = 0200;

System.out.println(num); // 128

System.out.println(033); // 27

Answer 1

Sure – it’s treating it as an octal literal, as per the Java Language Specification, section 3.10.1:

An octal numeral consists of an ASCII digit 0 followed by one or more of the ASCII digits 0 through 7 and can represent a positive, zero, or negative integer.

OctalNumeral:
        0 OctalDigits

OctalDigits:
        OctalDigit
        OctalDigit OctalDigits

OctalDigit: one of
        0 1 2 3 4 5 6 7

Note that octal numerals always consist of two or more digits; 0 is always considered to be a decimal numeral-not that it matters much in practice, for the numerals 0, 00, and 0x0 all represent exactly the same integer value.