public class UserService {

  private UserRepository userRepository;

  public UserService(UserRepository userRepository) {
    this.userRepository = userRepository;
  }

  public User getUserById(long id) {
    try {
      return userRepository.getUserById(id);
    } catch (Exception e) {
      // Log the exception here
      System.out.println("An error occurred while fetching the user: " + e.getMessage());
      return null;
    }
  }
}

public class UserRepository {

  public User getUserById(long id) throws Exception {
    // Database query to fetch the user
    if (id < 0) {
      throw new Exception("Invalid user id");
    }
    // Return the user object
    return new User(id, "John Doe");
  }
}

public class User {

  private long id;
  private String name;

  public User(long id, String name) {
    this.id = id;
    this.name = name;
  }

  public long getId() {
    return id;
  }

  public String getName() {
    return name;
  }
}

public class Factorial
{
	public static void main(String[] args)
	{	final int NUM_FACTS = 100;
		for(int i = 0; i < NUM_FACTS; i++)
			System.out.println( i + "! is " + factorial(i));
	}
	
	public static int factorial(int n)
	{	int result = 1;
		for(int i = 2; i <= n; i++)
			result *= i;
		return result;
	}
}

public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode head = new ListNode(0);
        ListNode handler = head;
        while(l1 != null && l2 != null) {
            if (l1.val <= l2.val) {
                handler.next = l1;
                l1 = l1.next;
            } else {
                handler.next = l2;
                l2 = l2.next;
            }
            handler = handler.next;
        }
        
        if (l1 != null) {
            handler.next = l1;
        } else if (l2 != null) {
            handler.next = l2;
        }
        
        return head.next;
    }
}

//sample code to write 100 random ints to a file, 1 per line

import java.io.PrintStream;
import java.io.IOException;
import java.io.File;

import java.util.Random;

public class WriteToFile {
    public static void main(String[] args) {
        try {
            PrintStream writer = new PrintStream(new File("randInts.txt"));
            Random r = new Random();
            final int LIMIT = 100;

            for (int i = 0; i < LIMIT; i++) {
                writer.println(r.nextInt());
            }
            writer.close();
        } catch (IOException e) {
            System.out.println("An error occured while trying to write to the file");
        }
    }
}

import java.util.Scanner;

/* In Heaven, the seed is tall and the oak small / It's input vital 
	* "The al-Madinatian," verse 236-37 
	* tinyurl.com/17snqkfv
	* email answer to [email protected]
	**/

public class Main
{
	public static void main(String args[])
	{
		int x = 0;
		int a, c, m = 10000;
		
		Scanner in = new Scanner(System.in);
		
		System.out.println("Please enter a seed, maximum 3000000:");
		x = in.nextInt();
		
		System.out.println("Please input a number, maximum 29:");
		a = in.nextInt();
		
		System.out.println("Please input a number, maximum 999999:");
		c = in.nextInt();
		
		char menu = 'y';
		while(menu != 'n')
		{
			x = (a*x + c) % m;
			
			System.out.println("The next number is " + x + "\nWould you like another? (y/n)");
			menu = in.next().charAt(0);
		}
	}
}

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//██║  ██╔══██╗████╗░████║  ██╔══██╗██╔══██╗██╔════╝██╔══██╗██╔══██╗██║░░░░░██║░░░██║██╔════╝
//██║  ███████║██╔████╔██║  ██║░░██║███████║█████╗░░██║░░██║███████║██║░░░░░██║░░░██║╚█████╗░
//██║  ██╔══██║██║╚██╔╝██║  ██║░░██║██╔══██║██╔══╝░░██║░░██║██╔══██║██║░░░░░██║░░░██║░╚═══██╗
//██║  ██║░░██║██║░╚═╝░██║  ██████╔╝██║░░██║███████╗██████╔╝██║░░██║███████╗╚██████╔╝██████╔╝
//╚═╝  ╚═╝░░╚═╝╚═╝░░░░░╚═╝  ╚═════╝░╚═╝░░╚═╝╚══════╝╚═════╝░╚═╝░░╚═╝╚══════╝░╚═════╝░╚═════╝░