Java中的左移0
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Left bit shift 0 in Java
提问by Riz
Consider:
考虑：
int a = 0;
a |= 1 << a;
System.out.println(a);
It prints "1". Why? I thought left bit shifting 0 by any number of times was still 0. Where's it pulling the 1 from?
它打印“1”。为什么？我认为将 0 左移任意次数仍然是 0。它从哪里拉出 1？
采纳答案by Mike Christensen
The expression 1 << a;will shift the value 1, anumber of times.
该表达式1 << a;将移动值1，a次数。
In other words, you have the value 1:
换句话说，您的值为 1：
0000001
Now, you shift the whole thing over 0 bits to the left. You then have:
现在，您将整个内容向左移动 0 位。然后你有：
0000001
You then have:
然后你有：
a |= 1 << a;
Which resolves to:
其解析为：
a = 0000000 | 0000001
Or:
或者：
a = 1;
You might have the operands mixed up. If you're trying to shift the value 0 one bit to the left, you'd want:
您可能混淆了操作数。如果您试图将值 0 向左移动一位，您需要：
a |= a << 1;
回答by nashuald
You are using the operator << in a wrong way. It must to be:
您以错误的方式使用运算符 << 。它必须是：
int a = 0;
a |= a << 1;
System.out.println(a);
回答by William Morrison
You are left shifting the literal 1by the variable a. The value of variable ais zero. 1<<0 = 1
您将文字左移1变量a。变量的值a为零。1<<0 = 1
So you've just got your variables flipped. Try reversing the variables.
所以你刚刚改变了你的变量。尝试反转变量。
