444444444>>>-5=3搞不懂原理

Question

444444444>>>-5=3
請問這個是什麽意思?
不明白-5表示什麽? 正數的話我就懂...

Answer 1

在官网文档http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.19
有如下一段话：
[quote]
If the promoted type of the left-hand operand is int, only the five lowest-order bits of the right-hand operand are used as the shift distance. It is as if the right-hand operand were subjected to a bitwise logical AND operator & (§15.22.1) with the mask value 0x1f (0b11111). The shift distance actually used is therefore always in the range 0 to 31, inclusive.

If the promoted type of the left-hand operand is long, then only the six lowest-order bits of the right-hand operand are used as the shift distance. It is as if the right-hand operand were subjected to a bitwise logical AND operator & (§15.22.1) with the mask value 0x3f (0b111111). The shift distance actually used is therefore always in the range 0 to 63, inclusive.
[/quote]

看来之前我说的mod方式有些不是很合理，以官网说的为准，他描述了左操作符如果是int则只取移位表达式补码的最后5位
如果是long则只取移位表达式补码的最后6位