Because the programme is supposed to return 0 if the input number is negative (less than zero).

why to check for if(n>=0) ?? Mine worked without that condition itself

just else will not work because if n=0 then the function will throw illegalargumentexception. your else if works best :)

thanks

Is it a good practice to use 'float' in 'for' loop for a unit incremental condition?

Using the same type of condition in two 'if' statements seems redundant. Just an 'else' would do just fine.

else if(n!=0){
throw new IllegalArgumentException("Oh no");
}

if ever you wanted to use the else-if condition

ooh. why is that? something to do with JVM? What do you mean by a functional language?