If you know exactly the number of input then use an Array, if not use a ArrayList

With Arrays

  String []inpupts = new String[b];
  for (int i=0; i< b; i++) {
      System.out.println("Enter a string: ");
      inputs[i] = in.nextLine();
  }

With ArrayList

  List<String> inpupts = new ArrayList<String>();
  for (int i=0; i< b; i++) {
      System.out.println("Enter a string: ");
      inputs.add(in.nextLine());
  }

If every input asks the same question, you should use a for loop and an array of inputs:

Scanner dd = new Scanner(System.in);
int[] vars = new int[3];

for(int i = 0; i < vars.length; i++) {
  System.out.println("Enter next var: ");
  vars[i] = dd.nextInt();
}

Or as Chip suggested, you can parse the input from one line:

Scanner in = new Scanner(System.in);
int[] vars = new int[3];

System.out.println("Enter "+vars.length+" vars: ");
for(int i = 0; i < vars.length; i++)
  vars[i] = in.nextInt();

You were on the right track, and what you did works. This is just a nicer and more flexible way of doing things.

First you will have to decide what is going to be considered The End Of User Input and then act upon that specific condition. In the little example below, if the User enters nothing then that will be considered the End Of User Input.

All the code numbers entered by the User are stored within a List Interface object. Rules have also been applied whereas all code numbers supplied must be numerical and eight digits in length. The String#matches() method is used for this along with a small Regular Expression (regex). Also, there can be no duplicate code numbers supplied, each code number must be unique.

When the User has finished entering the desired Code Numbers then those numbers are sorted in ascending order and displayed within the console window:

System.out.println("Enter the required code numbers (enter nothing when done): ");   
Scanner in = new Scanner(System.in);

List<String> codes = new ArrayList<>();
// Outer loop to keep asking for Code Numbers
while (true) {
    boolean isValid = false; // Flag to ensure a valid entry
    String codeLine = "";
    // inner loop to back up valitity before storing supplied code Number.
    while (!isValid) {    
        System.out.print("Code Line: --> ");
        codeLine = in.nextLine().trim();
        // Break out of this inner loop if nothing is supplied
        if (codeLine.isEmpty()) { break; } 
        // Is the supplied number all digits and are there 8 of them? 
        if (!codeLine.matches("^\\d{8}$")) {
            // No...
            System.err.println("Invalid Code Number! Try Again...");
        }
        // Has the supplied number already been previously stored?
        // In other words, is it unique?
        else if (codes.contains(codeLine)) {
            // Already got it! Not Unique!
            System.err.println("Code Number: " + codeLine + " has already been supplied!");
        }
        // Passed validity! Set isValid to true so to exit this inner loop.
        else { isValid = true; }
    }
    // Break out of the outer loop is nothing was supplied.
    if (codeLine.isEmpty()) { break; }
        
    // Validity has been met so Store the the supplied code number.
    codes.add(codeLine);
}
in.close(); // Close the input Stream
System.out.println("Scanner closed");
    
// Sort the Stored Code Numbers in ascending order.
Collections.sort(codes);
    
// Display the Stored Code Numbers...
System.out.println("Code Numbers Entered:");
System.out.println(codes);