如何使用增强的for循环初始化数组？

Question

I was optimizing an application and wanted to change my for loops to enhanced loops:

From:

for (int m = 1;m < MAX_BEREN;m++)
{           
    Wasberen[m] = new Wasbeer();       
    Wasberen[m].YYY = r.nextInt(SchermY - 28);
}

to:

for (Wasbeer a : Wasberen)
{
    if (a!=null)
    {
       a = new Wasbeer();
       a.YYY = r.nextInt(SchermY - 28);
    }
}

I get a NullPointerException, because it probably doesnt know how much 'beren' can be in the array, but I'm not sure how to manage the same as the loop above (MAX_BEREN = 11).

Answer 1

为了初始化数组，您应该坚持以前的语法。

Answer 2

如果增强的for语句中的数组引用（在这种情况下为“ Wasberen ”）为null，则在执行该语句时将导致NullPointerException 。

Answer 3

You can't use the enhanced for-loop in Java to fill an array. (I'm assuming your Wasberen array was already created before - if not, this will get you a NullPointerException in both variants.)

Your code (simplified)

for (Wasbeer a : Wasberen)
{
    a = ...;
}

is equivalent to

for (int i = 0; i < Wasberen.length; i++)
{
    Wasbeer a = Wasberen[i];
    a = ...;
}

This assignment will change the local variable a , but will have no effect on the contents of the array.