Java num=+10 和 num+=10 有什么区别？
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What's the difference between num=+10 and num+=10?
提问by user3102361
I am new to java, so while experimenting (which is, as you know, the best way to learn), I tried the following code:
我是 Java 新手，因此在进行实验时（如您所知，这是最好的学习方式），我尝试了以下代码：
public class wHilE{
public static void main(String[] args){
int num = 10;
while(num<=100){
System.out.println("while countdown = "+ num);
num=+10;
}
}
}
It results is an infinite loop printing while countdown = 10, but when I change num=+10to num+=10I get the desired result.
结果是无限循环打印while countdown = 10，但是当我更改为时num=+10，num+=10我得到了想要的结果。
Why is it so?
为什么会这样？
回答by dasblinkenlight
The +=is a compound assignment; the =+is a normal assignment, followed by a plus sign, which is optional for positive numbers:
的+=是这样的化合物分配; the=+是正常赋值，后跟一个加号，对于正数是可选的：
x += 10;
^ ^^ ^^
| | |
var | val
compound assignment
vs.
对比
x = +10;
^ ^ ^^^
| | |
var| val
assignment
The first operation adds ten to x; the second operation assigns 10 to xregardless of its prior value.
第一个操作将 10 添加到x; 第二个操作将 10 分配给x不管它的先前值。
回答by Eran
num=+10is equivalent to num=10. That's why the loop never ended.
num=+10相当于num=10。这就是循环从未结束的原因。
num+=10is equivalent to num=num+10, which gives you the desired behavior.
num+=10相当于num=num+10，它为您提供所需的行为。
回答by ronilp
num += 10means num = num + 10It will assign num + 10 value to num.
num += 10意味着num = num + 10它将为 num 分配 num + 10 值。
Whereas num=+10means num = +10which means +10 value will be stored in num.
+10 here means positive 10.
而num=+10意味着num = +10这意味着 +10 值将存储在 num 中。+10 这里的意思是正 10。
