Program Outputting Null Into Validation Statement - Runtime Error

I am Having trouble with my program to validate. It is outputting null into the validation statement then it brings back a run-time error to that validation Statement for the String.

public String validateData ()
{
if (nm == null)nm = "Error! Must enter at least one character";
else nm = name;
return name;
}//end validation method

Why is this happening, and then once that is completed, why is the validation Sentence in tests Scores not able to validate. I traced it back to out put "Error, a number between 1<100".

public void validateTests ()
{
String testschange;
if (test1 < 0 || test1 > 100) {
testschange = " You have entered an invalid number, between 1-100.
Please restart!";
testschange = Integer.toString( test1 ) ;

[Code] .....