“在网上有看到说byte、char等移位只针对低5位，long是针对低6位，真是这样吗？没法理解，好像也和测试不符。” 上面说法是对的。参考《The Java™ Language Specification Java SE 7 Edition》15.19 Shift OperatorsIf 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 lowestorder 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.
嗯，原来是我没有仔细看清，上面说的低5位，低6位是针对右操作数，即你要移动多少位来说的，并不是针对做操作数而言的。大家可以参考下这篇文章，觉得讲得蛮清楚的:http://www.360doc.com/content/07/1112/14/15458_818168.shtml. 其实问这么多就是想自己能够写出int转2进制，16进制的算法，发现还不是很理解。这个是jdk中int转2进制的算法，谁可以帮忙解释下算法：public static String toBinaryString(int i) { return toUnsignedString(i, 1); } /** * Convert the integer to an unsigned number. */ private static String toUnsignedString(int i, int shift) { char[] buf = new char[32]; int charPos = 32; int radix = 1 << shift; int mask = radix - 1; do { buf[--charPos] = digits[i & mask]; i >>>= shift; } while (i != 0); return new String(buf, charPos, (32 - charPos)); }
个人感觉转换为int型的含义是，先将待计算的参数转换为int，然后再进行计算。
所以你的第二点是对的
这应该没什么歧义吧?至于你的第一个观点,你没理解java的解释吧,是先转再移而不是先移再转
谢谢，但是我在网上有看到说byte、char等移位只针对低5位，long是针对低6位，否则会影响最终结果int的值，是这样吗？感觉好像都是从最高位开始移吧
上面说法是对的。参考《The Java™ Language
Specification
Java SE 7 Edition》15.19 Shift OperatorsIf 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 lowestorder
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.
嗯，原来是我没有仔细看清，上面说的低5位，低6位是针对右操作数，即你要移动多少位来说的，并不是针对做操作数而言的。大家可以参考下这篇文章，觉得讲得蛮清楚的:http://www.360doc.com/content/07/1112/14/15458_818168.shtml. 其实问这么多就是想自己能够写出int转2进制，16进制的算法，发现还不是很理解。这个是jdk中int转2进制的算法，谁可以帮忙解释下算法：public static String toBinaryString(int i)
{
return toUnsignedString(i, 1);
} /**
* Convert the integer to an unsigned number.
*/
private static String toUnsignedString(int i, int shift)
{
char[] buf = new char[32];
int charPos = 32;
int radix = 1 << shift;
int mask = radix - 1;
do
{
buf[--charPos] = digits[i & mask];
i >>>= shift;
} while (i != 0); return new String(buf, charPos, (32 - charPos));
}