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Newbie to Java trying to figure out how to jump BACK in a do-while loop if a certain input is given

This is the code I have at the moment and I am trying to figure out how to jump back up from case "A" to the top of the do-while loop to allow the user to selection another action. The idea is that the user would be able to check their balance and then go back after checking their balance and either top-up their card or buy a wash. I only know how to end the loop from this point, not how to jump backwards to the previous input.
do {
System.out.println("Please select an option:\nPress [A] to CHECK FUNDS, press [B] to TOP-UP CARD, press [C] to BUY WASH or press [Q] to quit.");
String actionSelection = scan.nextLine();
switch (actionSelection) { //I haven't defined all the cases yet! //The other cases should not need to refer to other classes, all the actions are within the WashCard
case "A":
System.out.println("Your current balance is: " + this.cardBalance + ".00 DKK.");
sentinel = true;
System.out.println("Would you like to do something else? Press [B] to go back or [Q] to quit.");
break;
case "B":
System.out.println("How much would you like to deposit?\nPlease type in a number between 200 and 1000.");
//user input
break;
case "C":
//any selection should display card balance
//insufficient funds conditional statement:
if (this.cardBalance < 50) {
sentinel = true;
System.out.println("Not enough credit! Please top-up your card first");
System.out.println("Your current balance is: " + this.cardBalance + ".00 DKK.");
}
//only 50 DKK left on the card:
else if (this.cardBalance == 50) {
sentinel = false;
System.out.println("You only have enough credit for the ECONOMY WASH.");
System.out.println("Your current balance is: " + this.cardBalance + ".00 DKK.");
}
//any other choice:
else {
sentinel = false;
System.out.println("Your current balance is: " + this.cardBalance + ".00 DKK.");
}
break;
default:
sentinel = true;
System.out.println("Please enter a valid input!");
}
} while ( sentinel == true );

You do not need this. This soulution breaks OOP pricniples. To solve it you should encapsulate different logic in different methods.
public class Foo {
public static void main(String... args) {
Scanner scan = new Scanner(System.in);
proceed(scan);
}
private static final char CHECK_FUNDS = 'A';
private static final char TOP_UP_CARD = 'B';
private static final char BUY_WASH = 'C';
private static final char QUIT = 'Q';
public static void proceed(Scanner scan) {
while (true) {
System.out.println("Please select an option:");
System.out.format("[%s] - CHECK FUNDS\n", CHECK_FUNDS);
System.out.format("[%s] - TOP-UP CARD\n", TOP_UP_CARD);
System.out.format("[%s] - BUY WASH\n", BUY_WASH);
System.out.format("[%s] - quit\n", QUIT);
System.out.print("> ");
String menu = scan.nextLine().toUpperCase();
char ch = menu.length() == 1 ? menu.charAt(0) : '\0';
if (ch == CHECK_FUNDS)
onCheckFunds();
else if (ch == TOP_UP_CARD)
onTopUpCard();
else if (ch == BUY_WASH)
onBuyWash();
else if (ch == QUIT)
return;
System.err.println("incorrect input");
}
}
private static void onCheckFunds() {
System.out.println("onCheckFunds");
}
private static void onTopUpCard() {
System.out.println("onCheckFunds");
}
private static void onBuyWash() {
System.out.println("onBuyWash");
}
}

How to loop main class

I am trying to make my rock paper scissors app loop if the user wants it to and am not sure how.
I am in a programming class but I broke my code while trying to fix it last time and managed to return to what I had before.
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
String playAgain = "Y";
while (playAgain.equals("Y") || playAgain.equals("y"))
{
String playerChoice = "";
while (!playerChoice.equals("R") && !playerChoice.equals("P") && !playerChoice.equals("S"))
{
System.out.println("Please enter a correct character\n (R)ock, (P)aper, or (S)cissors.");
playerChoice = scan.next();
//Player choice to upper case to minimize the number of wrong inputs//
playerChoice = playerChoice.toUpperCase();
}
int randNum = (int) (Math.random() * 3);
String compChoice = "";
switch (randNum)
{
case 0:
compChoice = "R";
break;
case 1:
compChoice = "P";
break;
case 2:
compChoice = "S";
break;
}
System.out.println("The computer chose: " + compChoice);
if (playerChoice.equals(compChoice))
{
System.out.println("It's a Tie!");
} else if (playerChoice.equals("R") && compChoice.equals("S") || playerChoice.equals("P") && compChoice.equals("R") || playerChoice.equals("S") && compChoice.equals("P"))
{
System.out.println("You Win!");
} else
{
System.out.println("You Lose");
}
System.out.println("Would you like to play again?\n(Y or N)");
playAgain = scan.nextLine();
if (playAgain.equals("N"))
{
break;
}
}
}

The solution is you need agreement between your scan method calls.
Either both should be nextLine or both should be next.
As an aside - I quite like the use of .equalsIgnoreCase instead of .equals on string comparisons, since it makes the code simple and easy to read. (You can skip the toUpperCase for instance, and the extra conditions)
As for why/what exactly the scanner is doing which causes that problem, that's a lot more detailed and fiddly.

Rock, paper, scissors game Invalid entry loop

I am trying to figure out where to put the loop that when the user enters any value other than "rock", "paper" or "scissors" the program stays in the loop and displays "Invalid entry" while requesting the user to enter again.
Any help is much appreciated.
As it stands now, the program will display "Invalid entry" but then continues without asking the user to try again.
import java.util.Scanner; // Import the Scanner class
import java.util.Random; // Import the random class for game
/**
*/
public class Challenge17
{
// Method to determine the random choice of computer
public static String getComputerChoice(Random random)
{
int number;
number = random.nextInt(3) + 1;
String computerChoice;
switch (number)
{
case 1:
computerChoice = "rock";
break;
case 2:
computerChoice = "paper";
break;
case 3:
computerChoice = "scissors";
break;
default:
computerChoice = "";
}
return computerChoice;
}
// Method to display the menu for choices
public static void displayChoice( )
{
System.out.println("Game Options\n----------\n"
+ "1: rock\n2: paper\n3: scissors");
}
// Method to request and hold user choice for game
public static String getUserInput(Scanner keyboard)
{
String userInput;
System.out.println("Enter your choice: ");
userInput = keyboard.nextLine();
return userInput;
}
// Method to determine winner
public static String determineWinner(String computerChoice, String userInput)
{
String winner = "Tie Game!"; // Default display Tie game
String message = ""; // To determine the message for winner
String displayMessage; // To display the message for winner
// Custom messages below
String rockMessage = "Rock smashes scissors";
String scissorsMessage = "Scissors cuts paper";
String paperMessage = "Paper wraps rock";
boolean loop = false;
if(computerChoice.equals("rock") && userInput.equalsIgnoreCase("scissors"))
{
winner = " Computer wins!";
message = rockMessage;
loop = true;
}
else if (userInput.equalsIgnoreCase("rock") && computerChoice.equals("scissors"))
{
winner = "You win!";
message = rockMessage;
loop = true;
}
if(computerChoice.equals("scissors") && userInput.equalsIgnoreCase("paper"))
{
winner = " Computer wins!";
message = scissorsMessage;
loop = true;
}
else if (userInput.equalsIgnoreCase("scissors") && computerChoice.equals("paper"))
{
winner = "You win!";
message = scissorsMessage;
loop = true;
}
if(computerChoice.equals("paper") && userInput.equalsIgnoreCase("rock"))
{
winner = " Computer wins!";
message = paperMessage;
loop = true;
}
else if (userInput.equalsIgnoreCase("rock") && computerChoice.equals("scissors"))
{
winner = "You win!";
message = paperMessage;
loop = true;
}
else
{
System.out.println("Invalid entry.");
loop = false;
}
displayMessage = winner + " " + message;
return displayMessage;
}
// Main method to initiate and execute game
public static void main(String[] args)
{
Random random = new Random(); // To call the random class
Scanner keyboard = new Scanner(System.in); // To call the scanner class
String computerChoice; // Hold computer input
String userInput; // Hold user input
String input; // Hold input for repeat
char repeat; // Character for repeat
do
{
displayChoice(); // Call method to display the choices
computerChoice = getComputerChoice(random); // Hold the PC random choice
userInput = getUserInput(keyboard); // To get the user input
System.out.println("You chose: " + userInput + " computer chose: \n"
+ computerChoice);
System.out.println(determineWinner(computerChoice, userInput));
// Does the user want to play again
System.out.println("Would you like to play again?");
System.out.print("Enter Y for yes, or N for no: ");
input = keyboard.nextLine();
repeat = input.charAt(0);
}
while (repeat == 'Y' || repeat == 'y');
}
}

From my understanding i'm pretty sure you want this kind of a loop
public static String getUserInput(Scanner keyboard)
{
String userInput;
System.out.println("Enter your choice: ");
userInput = keyboard.nextLine();
while(!userInput.equals("rock")&&!userInput.equals("paper")&&!userInput.equals("scissors"))
{
System.out.println("Invalid Entry, Please re-enter your choice:");
userInput = keyboard.nextLine();
} //It wont go out of the loop unless it's one of the 3 choices
return userInput;
}

You could create a Boolean method.
private Boolean checkUserInput(String input) {
if(!input.equalsIgnoreCase("rock") && !input.equalsIgnoreCase("paper") && !input.equalsIgnoreCase("scissors")) return false;
return true;
Then you do the check before you determine the winner like if true then run the determineWinner(computerChoice, userInput) code else it doesn't.
That way, you can edit the code and add functionalities in the future if need be.

Java rock paper scissor printing the statements oddly

So here i am trying to create a program that takes an input as an int and then plays a game of Rock paper scissors. It seems to want to reprint statements that it shouldn't be and is skipping printing statements as well. I would love some assistance if possible. I have tried setting up print statements everywhere but it has just been more confusing.
import java.util.Scanner;
public class RPSS{
//Main method
public static void main(String[ ] argc)
{
System.out.println("Lets play rock paper scissors");
Scanner tnt = new Scanner(System.in);
String computerHand; // string variable for computer choice
String userHand; // string variable for user choice
//
String answer = "";
while (!a
nswer.equals("No") && (!answer.equals("no"))){
userHand = userHand();
computerHand = computerHand();
System.out.println("The User picks " + userHand + " " );
System.out.print("The Computer picks " + computerHand );
String winner = getWinner(computerHand, userHand);
System.out.println(winner);
System.out.println("play again?");
answer = tnt.next();
}
//Condition for the do-while loop
}
public static String userHand(){ //method for users choice in the game
//prints message to user giving them choices
System.out.println(" ");
System.out.println("1. Rock ");
System.out.println("2. Paper ");
System.out.println("3. Scissors ");
int userChoice; // user choice variable in this method
Scanner tnt = new Scanner(System.in); // creates instance of scanner class
userChoice = tnt.nextInt(); //reads user input
return getChoice(userChoice); //returns user choice to userChoice
}
public static String computerHand() //method for computer generated choice
{
int computernum = 1 + (int)(Math.random() * (( 2) +1));
return getChoice(computernum);
}
public static String getChoice(int num) //method recieving both computer hand and user hand
{
// if statements to place the correct choice
String choice = "";
if (num == 1){
choice = "Rock";
}
else if(num == 2){
choice = "Paper";
}
else if(num == 3){
choice = "Scissors";
}
return choice;
}
// Method determing the winner
public static String getWinner(String computerChoice, String userChoice)
{
computerChoice = computerHand(); //places computerChoice variable in computerhand
userChoice = userHand(); //does same for user choice
String winner="";
if (userChoice.equals("Rock") && computerChoice.equals("Paper")){
System.out.println("The computer wins");
return winner;
}
else if (userChoice.equals("Paper") && computerChoice.equals("Scissors")){
System.out.println(" The computer wins");
return winner;
}
else if (userChoice.equals("Scissors") && computerChoice.equals("Rock")){
System.out.println(" The computer wins ");
return winner;
}
else if (userChoice.equals("Rock") && computerChoice.equals("Paper")){
System.out.println(" The computer wins ");
return winner;
}
else if(userChoice.equals(computerChoice))
{
System.out.println(" There is no winner");
return " ";
}
else{
return winner;
}
}
}

The first problem is that userhand() and computerHand() are being called twice per "round", once at the beginning of the while loop inside the main method and once at the beginning of the getWinner() method. Elimination of the calls at the beginning of the getWinner() method should solve the repeats.
The 2nd Problem is that instead of modifying the value of winner inside the getWinner() method before returning it, you are you are simply outputting the message via println(). an example of fixing this would be converting this:
if (userChoice.equals("Rock") && computerChoice.equals("Paper"){
System.out.println("The computer wins");
return winner;
}
to this:
if (userChoice.equals("Rock") && computerChoice.equals("Paper")){
winner = "The computer wins";
return winner;
}
another minor issue is the fact that
userChoice.equals("Rock") && computerChoice.equals("Paper")
is checked twice, id just remove the entire if else block based around the
2nd check of it
Lastly i would treat the final else clause as the player wins one and set winner to something like " The player wins "

JAVA: Why do I keep getting these runtime errors?

Wrote a roshambo program, ran it once, worked fine, ran it again and the following errors popped up:
RoShamBo!
Play Game
Show Score
Quit
1
Which do you choose?
Rock
Paper
Scissors
2
Which do you choose?
Rock
Paper
Scissors
Invalid Entry, Please Try Again.
Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at RoShamBo.getUserChoice(RoShamBo.java:82)
at RoShamBo.winner(RoShamBo.java:112)
at RoShamBo.main(RoShamBo.java:27)
not sure on how to deal with these type of errors, this my first time using methods so i'm thinking it has to do with how I called each method? please help.
thanks in advance.
import java.util.Scanner;
public class RoShamBo
{
public static void main(String[] args)
{
System.out.println("RoShamBo!");
System.out.println("1. Play Game");
System.out.println("2. Show Score");
System.out.println("3. Quit");
Scanner userInput = new Scanner(System.in);
if(userInput.hasNextInt())
{
int userIn = userInput.nextInt();
if(userIn == 1)
{
getUserChoice();
getCompChoice();
winner();
}
else if(userIn == 2)
{
scores();
}
else if(userIn == 3)
{
System.out.println("Qutiing: Final Score was: ");
scores();
userInput.close();
}
else
{
System.out.println("Invalid Entry, Please Try Again.");
userInput.next();
}
}
else
{
System.out.println("Invalid Entry, Please Try Again.");
userInput.next();
}
}
public static String getUserChoice()
{
// ask player for a move : playerMove
System.out.println("Which do you choose?");
System.out.println("1. Rock");
System.out.println("2. Paper");
System.out.println("3. Scissors");
Scanner input = new Scanner(System.in);
String userChoice = " ";
if (input.hasNextInt())
{
int userInput = input.nextInt();
switch(userInput)
{
case 1:
userChoice = "Rock";
break;
case 2:
userChoice = "Paper";
break;
case 3:
userChoice = "Scissors";
break;
}
}
else
{
System.out.println("Invalid Entry, Please Try Again.");
input.next();
}
input.close();
return userChoice;
}
private static String getCompChoice()
{
//Method for getting Computers move
int compChoice = (int) ( 1 + (Math.random() * 3));
String compMove = " ";
switch(compChoice)
{
case 1:
compMove = "Rock";
break;
case 2:
compMove = "Paper";
break;
case 3:
compMove = "Scissors";
break;
}
return compMove;
}
public static String winner()
{
String winnerIs = " ";
String comp = getCompChoice();
String user = getUserChoice();
if(user.equals("Rock") && comp.equals("Scissors") ||
user.equals("Paper") && comp.equals("Rock") ||
user.equals("Scissors") && comp.equals("Paper"))
{
System.out.println("You Win!");
}
else
{
System.out.println("You Lose");
}
return winnerIs;
}
public static void scores()
{
int compCount = 0;
int userCount = 0;
if (winner().equals("You Win!"))
{
userCount++;
}
else
{
compCount++;
}
System.out.println("Player = " + userCount );
System.out.println("Computer = " + compCount );
}
}

Probably here
{
System.out.println("Invalid Entry, Please Try Again.");
input.next();
}
you are doing a next() without checking for has*().

Your stack gives one hint.
at java.util.Scanner.next(Unknown Source).
and
Exception in thread "main" java.util.NoSuchElementException
Turning to the documentation here:
http://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#next%28%29
part that is of interest to you:
Throws:
NoSuchElementException - if no more tokens are available
You call .next()
but what do you want to read? Is there anything waiting in input buffer? Also, see my comment, meaning that your logic is busted.Rethink your game logic instead of fixing it.
Giving a complete answer that gets your code to run like it's supposed to would mean writing most of your code, I won't go that way. Instead, you should apply one of the most powerful debugging methods known to humans and do it yourself:
https://en.wikipedia.org/wiki/Rubber_duck_debugging
Good luck and enjoy ;)