java移位运算符困惑private static final long WORD_MASK 0xffffffffffffffffLpublic static void main
java移位运算符困惑
private static final long WORD_MASK = 0xffffffffffffffffL; public static void main(String[] args) { int toIndex=70; long lastWordMask = WORD_MASK >>> -toIndex; System.out.println(lastWordMask); }
为什么输出结果为63而将无符号右移改为>>结果为-1 [最优解释] http://www.ticmy.com/?p=46 [其他解释] 摘自java语言规范: The value of n >> s is n right-shifted s bit positions with sign-extension. The resulting value is ? n / 2s ?. For non-negative values of n, this is equivalent to truncating integer division, as computed by the integer division operator /, by two to the power s.
The value of n >>> s is n right-shifted s bit positions with zero-extension, where:
If n is positive, then the result is the same as that of n >> s.
If n is negative and the type of the left-hand operand is int, then the result is equal to that of the expression (n >> s) + (2 << ~s).
If n is negative and the type of the left-hand operand is long, then the result is equal to that of the expression (n >> s) + (2L << ~s). [其他解释] http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.19 [其他解释]
