Java 如何检查一个整数是否可以被3整除
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How to check if an integer can be divided by 3
提问by Leem
How to check if my integer can be divided by 3 as below:
如何检查我的整数是否可以除以 3，如下所示：
for(int i=0; i<24; i++){
//here, how to check if "i" can be divided by 3 completely(e.g. 3, 6, 15)?
}
采纳答案by Sebastian Wramba
回答by Talha Ahmed Khan
Use the MOD operator
使用 MOD 运算符
for(int i=0; i<24; i++){
if( i%3 == 0 )
// It is divisible by 3
}
回答by Dimitar Petrov
Check the remainder of i devided by 3
检查 i 除以 3 的余数
if (i % 3 == 0) {}
回答by Tim Meyer
if( i % 3 == 0 )
The % operator delivers you the rest of the division i / 3
% 运算符为您提供除 i / 3 的其余部分
回答by BudgieInWA
inside the loop:
循环内：
if (i%3 == 0)
// it can be divided by 3
%is called "mod" or "modulus" and gives you the remainder when dividing two numbers.
%被称为“mod”或“模数”，并在将两个数字相除时为您提供余数。
These are all true:
这些都是真的：
6 % 3 == 0
7 % 3 == 1
7 % 4 == 3
回答by Benny Tjia
if( i % 3 == 0 ){
System.out.println("can be divided by 3");
}else{
System.out.println("cant divide by 3");
}
Is this question for real?
这个问题是真的吗？
回答by Peter Lawrey
If you are using a loop, you can use the fact that every third number can be divided by 3.
如果您使用的是循环，则可以使用每三个数字可以被 3 除的事实。
for(int i = 0; i < 24; i += 3) {
System.out.println(i + " can be divided by 3");
System.out.println((i+1) + " cannot be divided by 3");
System.out.println((i+2) + " cannnot be divided by 3");
}
This avoids the need for a modulo and cuts the number of loops by a factor of 3.
这避免了对模数的需要，并将循环数减少了 3 倍。
回答by Thomas Mueller
Well, what you coulddo (it mightbe a bit faster; it is faster on my machine) is:
好吧，你可以做的（可能会快一点；在我的机器上更快）是：
boolean canBeDevidedBy3 = ((int) (i * 0x55555556L >> 30) & 3) == 0;
instead of
代替
boolean canBeDevidedBy3 = (i % 3) == 0;
However, the multiplication trick only works for -2 <= i <= 1610612735. This answer was inspired by this optimization question. But if I can give you a tip: use (i % 3) == 0. It's so much simpler, and will always work.
但是，乘法技巧仅适用于-2 <= i <= 1610612735。这个答案的灵感来自这个优化问题。但如果我可以给你一个提示：使用(i % 3) == 0. 它非常简单，并且将始终有效。
