The user must enter a string that is greater than 6 characters long

How can I code this using subroutines in java with a loop so if they don't get it right it keeps repeating till they do. This is all i have so far. The user must enter a string that is greater than 6 characters long.

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package containsmethod;

import java.util.*;  
import java.lang.String;  
import java.lang.Character;
import java.util.Scanner;
public class ContainsMethod {

    
   public static boolean isValid(String password) {

    if (password.length() < 6) {
    return false;
    } else {
    char c;
    for (int i = 0; i < password.length() -1; i ++) {
    c = password.charAt(i);
    if (!Character.isLetterOrDigit(c)) {
    return false;
    } else if (Character.isDigit(c)) { 
        return false;
            }
    }
    }
    return false;
   }

 
   
    
            
    public static void main (String [] args) {
    Scanner input = new Scanner (System.in);
    {
    System.out.print ("Please enter a string that is greater than 6 characters long. ");
    String password = input.next();
    if (isValid(password)) {
    System.out.println ("That is a valid string onto stage 2.");
    } 
    else 
    {
    System.out.println ("That is a invalid string. Try again.");
    }
    }

First of all, your isValid function never returns true, even the case that user enters a password that is greater than 6 characters. So you should update your method like that:

public static boolean isValid(String password) {
        if (password.length() < 6) {
            return false;
        } else {
            char c;
            for (int i = 0; i < password.length() - 1; i++) {
                c = password.charAt(i);
                if (!Character.isLetterOrDigit(c)) {
                    return false;
                } else if (Character.isDigit(c)) {
                    return false;
                }
            }
        }
        return true;
    }

Then, you can take the user input in a do-while loop. So if the password is invalid it will keep asking. Here is your updated main method:

public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        {
            String password;
            do {
                System.out.print("Please enter a string that is greater than 6 characters long. ");
                password = input.next();
                if (isValid(password)) {
                    System.out.println("That is a valid string onto stage 2.");
                } else {
                    System.out.println("That is a invalid string. Try again.");
                }
            }while (!isValid(password));
        }
    }