How to make sure user type valid value? If valid -- Proceed

Question

Me develop a java console program.
BufferedReader request = new BufferedReader(new InputStreamReader(System.in));
String strpollutantNumber;
int pollutantNumber;
System.out.print("Enter pollutant number >> ");
strpollutantNumber = request.readLine();
pollutantNumber = Integer.parseInt(strpollutantNumber);
I want to control my pollutant number and make it always valid. Let's say, pollutant number is between 1 to 4 only. If user press 5, system ask to re-enter valid value as follow
Your pollutant number is invalid. Please re-enter.
Enter pollutant number >>
Did i need using loop at
System.out.print("Enter pollutant number >> ");
strpollutantNumber = request.readLine();
pollutantNumber = Integer.parseInt(strpollutantNumber);
or something..
need help.

Answer 1

so far, i want to control user input using
while ( ......)
user must enter value >=0.31 and <=0.39. if user enter value=0.29, it means this value is out from >=0.31 and <=0.39. see below program
while(gramEmitted>=0.31 && gramEmitted<=0.39) {
System.out.print("Your grams emitted value is not valid ... Please re-enter \n");
System.out.print("Enter number of grams emitted per mile >> ");
strgramEmitted = request.readLine();
gramEmitted = Double.parseDouble(strgramEmitted);
i want user will prompt >> Your grams emitted value is not valid .. Please re-enter \n
Enter number of grams emitted per mile >>
what i've now is when user enter value=0.29, the program not prompt the user to re-enter the value again.
how to adjust
while(*gramEmitted>=0.31 && gramEmitted<=0.39*) {
System.out.print("Your grams emitted value is not valid ... Please re-enter \n");
System.out.print("Enter number of grams emitted per mile >> ");
strgramEmitted = request.readLine();
gramEmitted = Double.parseDouble(strgramEmitted);
Edited by: Delinda on Oct 21, 2008 11:26 PM