Java 中的管道 (|) 运算符
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Pipe (|) operator in Java
提问by bentham
I've got this statement in Java:
我在 Java 中有这样的声明：
System.out.println(3|4);
Why is the output 7?
为什么输出是7？
采纳答案by Jonathon Faust
It's a bitwise OR operation. It's modifying things at a binary level.
这是一个按位或运算。它正在二进制级别修改事物。
011 3
in binary: | 100 in decimal: | 4
___ ___
111 7
Open Windows calc using scientific mode. You can flip between decimal and binary (and hex) and perform bitwise operations including or, and, xor, etc.
使用科学模式打开 Windows calc。您可以在十进制和二进制（和十六进制）之间切换，并执行按位运算，包括或、和、异或等。
To do a bitwise or in your head or on paper, compare each digit of the same ordinal. If either number is a 1, the result at that ordinal will be 1.
要按位或在头脑中或在纸上进行，请比较相同序数的每个数字。如果任一数字为 1，则该序号的结果将为 1。
回答by dcp
It's doing a bitwise ORoperation, and 3 OR4 is 7.
它在做一个bitwise OR操作，3 OR4 是 7。
回答by Mike Daniels
The operator |does a "bitwise OR". The output of bitwise OR on two bits is 1 if either bit is 1 or 0 if both bits are 0. Bitwise OR on two numbers just does a bitwise OR on each bit individually.
运算符|执行“按位或”。如果任一位为 1，则两位的按位 OR 的输出为 1，如果两位均为 0，则为 0。两个数字上的按位 OR 仅对每个位分别进行按位或运算。
Heres how 3|4works:
这是如何3|4工作的：
3: 00000011
4: 00000100
--------------
3|4: 00000111 = 7
回答by Mike Daniels
| is the "bitwise or" operator. in a|b, if nth bit of a and/or b is 1, the nth bit of the result will be 1. 3 is 11 in binary. 4 is 100 in binary.
| 是“按位或”运算符。在 a|b 中，如果 a 和/或 b 的第 n 位为 1，则结果的第 n 位将为 1。3 是二进制的 11。4 是二进制的 100。
0 1 1
or or or
1 0 0
= = =
1 1 1
And 111 happens to be the binary representation of 7.
而 111 恰好是 7 的二进制表示。
回答by davbryn
Binary representation:
二进制表示：
3 = 00000011
4 = 00000100
| is bitwise OR operator
when you OR two numbers, you take the binary representation and the OR result is 1 IFF for that column at least one column is set true (1)
当您对两个数字进行 OR 运算时，您采用二进制表示形式，并且该列的 OR 结果为 1 IFF 至少有一列设置为 true (1)
So
所以
00000011
00000100
--------
00000111
then, columns tell you the value at that position:
然后，列会告诉您该位置的值：
128, 64, 32, 16, 8, 4, 2, 1
so
所以
128, 64, 32, 16, 8, 4, 2, 1
0 , 0, 0, 0, 0, 1, 1, 1
any column with a 1 means you add that column's value:
任何带有 1 的列表示您添加该列的值：
4 + 2 + 1 = 7
回答by Jimmy Hoffa
As bitwise operators can be a little confusing without something to correlate them to, the way I've explained their function to non-programmers even is that you simply subtitute 1 for true and 0 for false, and then they behave identically to the operators in the english language:
由于按位运算符可能会有点混乱，没有将它们关联起来，我向非程序员解释它们的功能的方式甚至是你简单地用 1 代替真，用 0 代替假，然后它们的行为与 中的运算符相同英语这门语言：
the moon is blue AND the sky is blue, is false
月亮是蓝色的，天空是蓝色的，是假的
0 and 1 is 0
0 和 1 是 0
the moon is blue OR the sky is blue, is true
月亮是蓝色的或天空是蓝色的，这是真的
0 or 1 is 1
0 或 1 是 1
but the analogy breaks down when I get to:
但是当我到达时，这个类比就不成立了：
the ocean is blue XOR the trees are green, is false
海洋是蓝色的异或树是绿色的，是假的
回答by Aaron Anodide
It's useful to realize there is a generalized system for counting underlying this. Binary is base-2. Familiar decimal is base-10. Linux permission octal is base 8.
意识到在此基础上有一个通用的计数系统是很有用的。二进制是基数为 2。熟悉的十进制是基数为 10。Linux 权限八进制是基数 8。
A number's value is obtained by adding together the individual values of each of its digits. For any digit, the value is derived from a simple formula.
数字的值是通过将每个数字的各个值加在一起而获得的。对于任何数字，该值都来自一个简单的公式。
(digit) * (base) ^ (number of places to the left of the decimal point)
(digit) * (base) ^ (小数点左边的位数)
123 = one hundred and twenty three = (1 * 10^2) + (2 * 10^1) + (3 * 10^0) = 100 + 20 + 3
123 = 123 = (1 * 10^2) + (2 * 10^1) + (3 * 10^0) = 100 + 20 + 3
I learned that in CS211 (not bragging, just remembering)
我在 CS211 中了解到（不是吹牛，只是记住）
