How to make a condition block in java execute only once?

Consider a file reading scenario, where the first line is a header. When looping the file line by line, an 'if condition' would be used to check whether the current line is the first line.

for(Line line : Lines)
{
     if(firstLine)
     {
         //parse the headers
     }else
     {
         //parse the body
     }
}

Now since the control has come inside the 'if block', in all the other occurrences, it is waste to check the 'if condition'.

Is there any concept in java so that, once after executing, the particular line of code just vanishes away?

I think this would be a great feature if introduced or does it already exist?