int与前导0的行为奇怪[重复](int with leading 0's behave strangely [duplicate])

int与前导0的行为奇怪[重复](int with leading 0's behave strangely [duplicate]) java

可能重复： 整数与前导零

有人可以告诉我这里发生了什么吗？ 当我用前导零初始化一个int时，程序不会忽略这些零，而是执行一些我不知道的操作。

int num = 0200; println(num); // 128 println(0); // 27

Possible Duplicate: 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; println(num); // 128 println(0); // 27

最满意答案

当然 - 按照Java语言规范第.10.1节的规定 ，它将它视为八进制文字：

八进制数字由一个ASCII数字0和一个或多个ASCII数字0到7组成，可以表示正整数，零整数或负整数。

Octalumeral: 0 OctalDigits OctalDigits: OctalDigit OctalDigit OctalDigits OctalDigit: one of 0 1 2 4 5 6 7

请注意，八进制数字总是由两位或更多位组成; 0总是被认为是一个十进制数字 - 实际上并不重要，因为数字0，00和0x0都表示完全相同的整数值。

Sure - it's treating it as an octal literal, as per the Java Language Specification, section .10.1:

An octal numeral cists 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.

Octalumeral: 0 OctalDigits OctalDigits: OctalDigit OctalDigit OctalDigits OctalDigit: one of 0 1 2 4 5 6 7

ote that octal numerals always cist of two or more digits; 0 is always cidered 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.