Rock Paper Scissors Game Java

Question

I m new to programming and I m trying to write a very simple Rock  Paper  Scissors game in Java  It will compile and run fine  but I am looking to say something like  Invalid move  Try again   or something along those lines for when the user  personPlay  does not enter a correct character  r  p  or s   What would be the best way to do so  For example  if you enter a  q   it should print  Invalid move   Thank you so much in advance                       Rock java                     import java util Scanner   import java util Random     public class Rock     public static void main String   args          String personPlay    User s play --  R    P   or  S       String computerPlay         Computer s play --  R    P   or  S       int computerInt    Randomly generated number used to determine                         computer s play      String response         Scanner scan   new Scanner System in        Random generator   new Random          System out println  Hey  let s play Rock  Paper  Scissors  n                             Please enter a move  n     Rock   R  Paper                               P  and Scissors   S          System out println           Generate computer s play  0 1 2       computerInt   generator nextInt 3  1          Translate computer s randomly generated play to        string using if   statements       if  computerInt    1          computerPlay    R        else if  computerInt    2          computerPlay    P        else if  computerInt    3          computerPlay    S            Get player s play from input-- note that this is         stored as a string      System out println  Enter your play           personPlay   scan next           Make player s play uppercase for ease of comparison      personPlay   personPlay toUpperCase            Print computer s play      System out println  Computer play is      computerPlay            See who won  Use nested ifs       if  personPlay equals computerPlay           System out println  It s a tie          else if  personPlay equals  R            if  computerPlay equals  S               System out println  Rock crushes scissors  You win          else if  computerPlay equals  P                 System out println  Paper eats rock  You lose           else if  personPlay equals  P            if  computerPlay equals  S            System out println  Scissor cuts paper  You lose           else if  computerPlay equals  R                 System out println  Paper eats rock  You win           else if  personPlay equals  S              if  computerPlay equals  P              System out println  Scissor cuts paper  You win           else if  computerPlay equals  R                 System out println  Rock breaks scissors  You lose           else           System out println  Invalid user input

User · Answer

Before we try to solve the invalid character problem, the lack of curly braces around the if and else if statements is wreaking havoc on your program's logic. Change it to this:

if (personPlay.equals(computerPlay)) {
   System.out.println("It's a tie!");
}
else if (personPlay.equals("R")) {
   if (computerPlay.equals("S")) 
      System.out.println("Rock crushes scissors. You win!!");
   else if (computerPlay.equals("P")) 
        System.out.println("Paper eats rock. You lose!!");
}
else if (personPlay.equals("P")) {
   if (computerPlay.equals("S")) 
       System.out.println("Scissor cuts paper. You lose!!"); 
   else if (computerPlay.equals("R")) 
        System.out.println("Paper eats rock. You win!!");
} 
else if (personPlay.equals("S")) {
     if (computerPlay.equals("P")) 
         System.out.println("Scissor cuts paper. You win!!"); 
     else if (computerPlay.equals("R")) 
        System.out.println("Rock breaks scissors. You lose!!");
}
else 
     System.out.println("Invalid user input.");

Much clearer! It's now actually a piece of cake to catch the bad characters. You need to move the else statement to somewhere that will catch the errors before you attempt to process anything else. So change everything to:

if( /* insert your check for bad characters here */ ) { 
     System.out.println("Invalid user input.");
}
else if (personPlay.equals(computerPlay)) {
   System.out.println("It's a tie!");
}
else if (personPlay.equals("R")) {
   if (computerPlay.equals("S")) 
      System.out.println("Rock crushes scissors. You win!!");
   else if (computerPlay.equals("P")) 
        System.out.println("Paper eats rock. You lose!!");
}
else if (personPlay.equals("P")) {
   if (computerPlay.equals("S")) 
       System.out.println("Scissor cuts paper. You lose!!"); 
   else if (computerPlay.equals("R")) 
        System.out.println("Paper eats rock. You win!!");
} 
else if (personPlay.equals("S")) {
     if (computerPlay.equals("P")) 
         System.out.println("Scissor cuts paper. You win!!"); 
     else if (computerPlay.equals("R")) 
        System.out.println("Rock breaks scissors. You lose!!");
}

User · Answer

Why not check for what the user entered and then ask the user to enter correct input again   eg     Get player s play from input-- note that this is     stored as a string  System out println  Enter your play       response   scan next    if response   R   response   P   response   S      personPlay   response   else    System out println  Invaild Input       for the other modifications  please check my total code at pastebin

User · Answer

You could insert something like this   personPlay    B    while   personPlay equals  R    amp  amp   personPlay equals  P    amp  amp   personPlay equals  S             Get player s play from input-- note that this is         stored as a string      System out println  Enter your play           personPlay   scan next           Make player s play uppercase for ease of comparison      personPlay   personPlay toUpperCase         if   personPlay equals  R    amp  amp   personPlay equals  P    amp  amp   personPlay equals  S            System out println  Invalid move  Try again

User · Answer

I would recommend making Rock  Paper and Scissors objects   The objects would have the logic of both translating to from Strings and also  knowing  what beats what   The Java enum is perfect for this   public enum Type     ROCK  PAPER  SCISSOR     public static Type parseType String value          if  else logic here to return either ROCK  PAPER or SCISSOR         if value is not either  you can return null         The parseType method can return null if the String is not a valid type   And you code can check if the value is null and if so  print  invalid try again  and loop back to re-read the Scanner   Type person null    while person  null         System out println  Enter your play             person  Type parseType scan next           if person   null            System out println  invalid try again                 Furthermore  your type enum can determine what beats what by having each Type object know   public enum Type                    each type will implement this method differently     public abstract boolean beats Type other         each type will implement this method differently to see what beats what   ROCK       Override    public boolean beats Type other                       return other     SCISSOR                  Then in your code   Type person  computer     if  person equals computer       System out println  It s a tie        else if person beats computer         System out println person    beats     computer    You win          else       System out println computer     beats     person   You lose

User · Answer

int w  0   l  0  d 0  i 0      Scanner sc   new Scanner System in       try tentimes     while  i lt 10              System out println  scissor 1   Rock 2  Paper 3              int n   sc nextInt            int m   int  Math random   3 1             if n  m                System out println  Com   m   so gt  gt  gt       draw                d               else if   n-1  3   m 3                w                System out println  Com   m   so gt  gt  gt      win                      else if n  gt  4                         System out println  pleas enter correct number                     else               System out println  Com   m   so gt  gt  gt      lose                l                       i

[java] Rock, Paper, Scissors Game Java

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