help i need to create a java application using jgrasp that Continue to prompt the user for data as long as The Zipcode is not numeric or if the user input letters on the Zipcode

public class PrepareTax {

public static void main(String[] args) {

// TODO Auto-generated method stub

//Create object for Scanner

Scanner input=new Scanner(System.in);

//prompt user of tax file number

System.out.print("Enter the tax file number in the format of 999-999-999:");

String tfn=input.next();

/*verify valid or invalid*/

while(!isValidNumber(tfn)){

System.out.print("Enter the valid tax file number:");

tfn=input.next();

}//end while

//prompt the user of the last name

System.out.print("Enter the last name:");

String last=input.next();

//prompt the user of the first name

System.out.print("Enter the first name:");

String first=input.next();

//prompt the user of street name

System.out.print("Enter your address ");

String strt=input.next();

//prompt the user of city name

System.out.print("Enter the city name:");

String cty=input.next();

//prompt the state name

System.out.print("Enter the state name:");

String st=input.next();

//prompt the Zip code

System.out.print("Enter the zip code:");

int zipCode=input.nextInt();

//verify the zip code

while(zipCode<1000||zipCode>9999){

System.out.print("Enter the valid zip code:");

zipCode=input.nextInt();

}//end while

System.out.print("Enter the annual income:$");

double income=input.nextDouble();

//verify annual income

while(income<0){

System.out.print("Enter the valid annual income:$");

income=input.nextDouble();

}//end while

//prompt the user for the marital status

System.out.print("Enter the marital status:");

char ms=input.next().charAt(0);

//verify marital status

while(ms!='S'&&ms!='s'&&ms!='M'&&ms!='m'){

System.out.print("Enter the valid marital status:");

ms=input.next().charAt(0);

}//end while

//create object for TaxReturn class

TaxReturn tr=new TaxReturn(tfn,last,first,strt,cty,st,zipCode,income,ms);

//call to displayData method

tr.displayData();

}//end of main method

//isValidNumber

private static boolean isValidNumber(String tfn){

//verify the length

if(tfn.length()!=11)

return false;

else{

/*repeat loop*/

for(int i=0;i

/*return false if the character'-is not at the proper place*/

if((i==3||i==7)&&tfn.charAt(i)!='-')

return false;

/*return false if any of the character in not the digit*/

if(i!=3&&i!=7&&!Character.isDigit(tfn.charAt(i)))

return false;

}//end

//return true if the number is valid

return true;

}//end if/else

}//end isValidNumber method

}//end of PreTax class