++ Var和Var ++之间的区别 [英] The difference between ++Var and Var++

问题描述

在编程中，特别是在Java中，有什么区别：

In programming, particularly in Java, what is the difference between:

int var = 0;
var++;

和

int var = 0;
++var;

这会对for循环产生什么影响？

What repercussions would this have on a for loop?

例如

for (int i = 0; i < 10; i++) {}

for (int i = 0; i < 10; ++i) {}

推荐答案

tldr;

虽然 var ++ 和 ++ var 增加它们应用的变量， var ++ 返回的结果是增量前变量的值，而返回的结果是 ++ var 是应用增量后变量的值。

tldr;

Although both var++ and ++var increment the variable they are applied to, the result returned by var++ is the value of the variable before incrementing, whereas the result returned by ++var is the value of the variable after the increment is applied.

当 ++ var 或 var ++ 形成一个完整的陈述（如在你的例子）两者之间没有区别。例如以下

When ++var or var++ form a complete statement (as in your examples) there is no difference between the two. For example the following

int x = 6;
++x;
assert x == 7;

与

int x = 6;
x++;
assert x == 7;

然而，当 ++ var 或 var ++ 用作较大语句的一部分，两者可能不等同。例如，以下断言传递

However, when ++var or var++ are used as part of a larger statement, the two may not be equivalent. For example, the following assertion passes

int x = 6;
assert ++x == 7;

而这一次失败

int x = 6;
assert x++ == 7;

虽然 var ++ 和 ++ var 递增它们应用的变量， var ++ 返回的结果是递增前变量的值，而 ++ var 返回的结果是应用增量后变量的值。

Although both var++ and ++var increment the variable they are applied to, the result returned by var++ is the value of the variable before incrementing, whereas the result returned by ++var is the value of the variable after the increment is applied.

当在中用于循环时，两者之间没有区别，因为变量的增量不构成较大语句的一部分。它可能不会以这种方式出现，因为源文件的同一行上还有其他代码。但是如果你仔细观察，你会发现在增量之前有一个; ，之后没有任何内容，所以增量运算符不构成一个更大的语句的一部分。

When used in a for loop, there is no difference between the two because the incrementation of the variable does not form part of a larger statement. It may not appear this way, because there is other code on the same line of the source file. But if you look closely, you'll see there is a ; immediately before the increment and nothing afterwards, so the increment operator does not form part of a larger statement.

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