Java-For循环中的2-Do-While循环

Question

I'm quite new to programming so excuse my basic and limited understanding. Essentially, I am creating a Memory Game for a school project. I want to do 2 do-while loops in a for loop that works like this: the user will be prompted to enter a 4 random letters which will be done in the first do-while loop and the second do-while loop will ask the user to re-input the phrase that they had initially entered.

So my first question is, why does only the first do-while execute? I'm assuming that the for loop executes the first-do-while and than repeats based on my parameters therefore the second one will never execute but, I'd appreciate any help understanding why, and reformatting my program accordingly perhaps.

My second question is that, I want to have a sort of score counter that nets the user 10 points for every correctly guessed letter in the correct sequence and deduct 10 for every incorrect character in the wrong sequence. How would I go about doing so, and what may I have to utilize to make this possible?

Lastly, I would appreciate if anyone could point towards a way of concealing the letters that the user inputs.

Any other suggestions to make my program more efficient would be greatly appreciated!

import java.util.Scanner;
import java.lang.String;

public class MemoryGame { 
public static void main(String[]args){
Scanner input = new Scanner(System.in); 
int choice;

System.out.println("This is a M E M O R Y  G A M E"); 
System.out.println("Press '1' for instructions");
System.out.println("Press '2' to play");

choice = input.nextInt(); //Checks user selection and redirects
if (choice == 1) {
  Instructions();
} else {
  playGame();
}
input.close();
}

public static void Instructions() { //Instructions method
int choice; 
Scanner input = new Scanner(System.in);

System.out.println("This is a memory game. Below are a few instructions     on how to play as well as few hints, and tricks");
System.out.println("> Players wlll be given a input box to input a given number of letters or numbers depending on the stage level.");
System.out.println("> To progress and gain points, users must sucessfully recall the set phrase that they have inputted.");
System.out.println("> Based on the number of correct letters, users will gain points and progress through a set of levels that increase in difficulty.");
System.out.println("> Upon making 3 incorrect character selections users will be displayed a 'Game Over' screen from which they may:");
System.out.println("1. Head to the main menu");
System.out.println("2. View the instructions");
System.out.println("3. Play again");
System.out.println("If users successfully oomplete 5 stages with no errors, they will be prompted a challenge level in which more characters will be required");
System.out.println(" ");
System.out.println("1. Press '1' to return to play");

choice = input.nextInt(); 
if (choice == 1) {
  playGame();
}
input.close(); //Closes input. 
}

public static void playGame() { 
int userNumbers1; 
int userNumbers2; 
String userLetters1;
String userLetters2;
int scorePlayer;
int livesPlayer = 3;
int stagePlayer = 4;
int stageGeneral = 1;
Scanner input = new Scanner(System.in);

System.out.println("This is the M E M O R Y  G A M E");
System.out.println("Stage 1 initializing . . .");
System.out.println("Please enter " + stagePlayer + " letters of your   choice.");

for (int i = 0; i <= 10; i++) {

do {
userLetters1 = input.nextLine();
userLetters1 = userLetters1.toLowerCase(); userLetters1.trim();
if (userLetters1.length()==stagePlayer) {
  System.out.println (". . .!");  
  stagePlayer = stagePlayer + 2;
  stageGeneral = stageGeneral + 1;
} else {
  System.out.println("Please enter " + stagePlayer + " letters");
}
}
while ( userLetters1.length() != stagePlayer);

do {
userLetters2 = input.nextLine();
userLetters2 = userLetters2.toLowerCase(); userLetters2.trim();
if (userLetters2.length()==userLetters1.length() && userLetters2.equals (userLetters1)) {
  System.out.println (". . .");
  System.out.println ("Great job!");
  System.out.println("Stage " + stageGeneral + " initializing . . .");
  System.out.println("Please enter " + stagePlayer + " letters of your choice.");
} else {
  System.out.println ("Please enter " + userLetters1.length() + "letters that were previously entered.");
}
}
while ( userLetters1.length() != userLetters2.length());
}
}
}

Answer 1

Don't assume. Debug instead. Look what happens line by line and determine the reason the first do lop never exits. It if exited I see no reason why the second one didn't execute.

For second question I'd enciurage to read String class documentation. All you need is to iterate through characters and react accordingly to results of copmarisions.

In console, to hide previous user input you could clear the screen like:

Runtime.getRuntime().exex("cls);