有很大的不同。
由于大多数答案已经指出了这个理论，我想指出一个简单的例子：

int x = 1;
//would print 1 as first statement will x = x and then x will increase
int x = x++;
System.out.println(x);

现在让我们看看 ++x :

int x = 1;
//would print 2 as first statement will increment x and then x will be stored
int x = ++x;
System.out.println(x);