我不明白为什么这个简单的声明不起作用

Question

So I'm basically finished with a program, and at the end of it I'm printing Strings from an array to a file. The array may contain null values, so I'm checking for null before I print, but I keep ending up with 1 null at the very end of the file...

Here's the code I'm using to check for null

for(int i=0;i<array2.length;i++)
{
    if(array2[i] != null)
        out.println(array2[i]);
}

I know that the array contains multiple instances of null, but only 1 is being printed. I tried using the debugger and when array2[i] == null, it still entered the conditional statement...

So I added a println statement to help me see what's going on. It now looks like this:

for(int i=0;i<array2.length;i++)
        {
            if(array2[i] != null)
            {
                System.out.println("Adding " + array2[i]);
                out.println(array2[i]);
            }

Just after printing all the String values to the console, it prints "Adding null" so I know it's happening here in this if statement. Why is this happening???

Answer 1

The debugger is not always clear as to whether it has entered an if condition or not. I don't believe this code is entering the if condition which it might appear it is and your null is probably coming from another line of code.

You could write the code as

for(ElementType e: array2.length)
    if(e != null)
        out.println("[" + e+ ']'); // extra text for debugging.
// I suspect your `null` will still be on a line of its own

Answer 2

Arent you also missing a set of brakets for the if statement??

for(int i=0;i<array2.length;i++) 
{ 
  if(array2[i] != null) 
  {
    out.println(array2[i]); 
  }
}