如何比較字符串與整數？

Question

如何比較字符串與int？我正在製作一款Rock-paper-scissors遊戲，如何將用戶輸入的字符串轉換爲int，以便程序可以檢查誰贏了？如用戶輸入「搖滾」程序註冊爲等？

package rpc; 

import java.util.Random; 
import java.util.Scanner; 

public class Main { 
    public static void main(String[] args) { 
     /* Random number generator */ 
     Random random = new Random(); 

     /* Scanner object for input */ 
     Scanner scanner = new Scanner(System.in); 

     /* 
     * Integer variables to hold the user and computer choice. 
     * 0 = Rock 
     * 1 = Paper 
     * 2 = Scissors 
     */ 
     String userChoice; 
     int computerChoice; 

     // Showing prompt and user input 
     System.out.println("Enter move (0 = Rock; 1 = Paper; 2 = Scissors):"); 
     userChoice = scanner.nextLine(); 

     // Checking if userChoice is 0, 1, or 2. 
     if (!userChoice.equalsIgnoreCase("Scissors") && !userChoice.equalsIgnoreCase("Paper") 
      && !userChoice.equalsIgnoreCase("rock")) { 
      System.out.println("Invalid choice. Ending program."); 

      // Exit program 
      Main.main(args); 
     } 

     // Generating random computer choice 
     computerChoice = random.nextInt(3); 

     // Determining the winner 

     // If the choices are equal, it's a tie. 
     if (userChoice == computerChoice) { 
      if (userChoice == 0) { 
       System.out.println("Both players chose rock!"); 
      } else if (userChoice == 1) { 
       System.out.println("Both players chose paper!"); 
      } else { 
       System.out.println("Both players chose scissors!"); 
      } 

      // Exit program 
      System.exit(0); 
     } 

     if (userChoice == 0) {  // User chooses rock 
      if (computerChoice == 1) { 
       System.out.println("You chose rock; Computer chose paper"); 
       System.out.println("Computer wins!"); 
      } else { 
       System.out.println("You chose rock; Computer chose scissors"); 
       System.out.println("You win!"); 
      } 
     } else if (userChoice == 1) { // User chooses paper 
      if (computerChoice == 0) { 
       System.out.println("You chose paper; Computer chose rock"); 
       System.out.println("You win!"); 
      } else { 
       System.out.println("You chose paper; Computer chose scissors"); 
       System.out.println("Computer wins!"); 
      } 
     } else { // User chooses scissors 
      if (computerChoice == 0) { 
       System.out.println("You chose scissors; Computer chose rock"); 
       System.out.println("Computer wins!"); 
      } else { 
       System.out.println("You chose scissors; Computer chose paper"); 
       System.out.println("You win!"); 
      } 
     } 
     scanner.close(); 
    } 
} 

Answer 1

只需使用pareseInt和字符串轉換爲int

對於前：

if(Integer.parseInt(userChoice) == computerChoice) 

確保輸入是不是null formattable爲int

編輯：改變parese到解析

Answer 2

Retrieving a random item from ArrayList

這不是你的問題的確切答案（Integer.parseInt（myInt）），但你可以嘗試更像這樣的可讀性，避免使用不必要的整數。並簡化您的代碼

生成您的arrayList，然後選擇隨機「計算機」的選擇。

List<String> posibilities = Arrays.asList("rock","paper","scissors"); 
String computerChoice = possibilites.get(Math.random(3)); 

然後做你的comparaison;）

/* Chose the possibilities */ 
List<String> posibilities = Arrays.asList("rock","paper","scissors"); 

/* Scanner object for input */ 
Scanner scanner = new Scanner(System.in); 

// Showing prompt and user input 
System.out.println("Enter move (0 = Rock; 1 = Paper; 2 = Scissors):"); 
String userChoice = scanner.nextLine(); 
userChoice = possibilities.get(Integer.parseInt(userChoice)); 

// Checking if userChoice is 0, 1, or 2. 
if(!possibilities.contains(userChoice)) { 
    System.out.println("Invalid choice. Ending program."); 

    // Exit program 
    Main.main(args); 
} 

// Generating random computer choice 
String computerChoice = possibilites.get(Math.random(3)); 

// Determining the winner 

// If the choices are equal, it's a tie. 
if(userChoice.equals(computerChoice)) { 
    System.out.println("Both players chose " + userChoice); 

    // Exit program 
    System.exit(0); 
} 

System.out.println("You chose " + userChoice + "; Computer chose " + computerChoice); 
if(userChoice.equals("rock")) { // User chooses rock 
    if(computerChoice.equals("paper")) { 
      System.out.println("Computer wins!"); 
    } else { 
     System.out.println("You win!"); 
    } 
} 
else if(userChoice.equals("paper")) { // User chooses paper 
    if(computerChoice.equals("rock")) { 
     System.out.println("You win!"); 
    } else { 
     System.out.println("Computer wins!"); 
    } 
} else { // User chooses scissors 
    if(computerChoice.equals("Scissors")) { 
     System.out.println("Computer wins!"); 
    } else { 
     System.out.println("You win!"); 
    } 
} 

scanner.close(); 

Answer 3

使用的Integer.parseInt方法解析字符串爲int，然後比較其

Answer 4

你可以使用一個枚舉列舉的三種可能選擇：

enum Hand { 

    ROCK, 
    PAPER, 
    SCISSORS; 

    public static Hand from(String input) { 
     for (Hand hand : values()) { 
      if (hand.name().equalsIgnoreCase(input)) { 
       return hand; 
      } 
     } 
     throw new IllegalArgumentException("Invalid choice: " + input); 
    } 

} 

枚舉有一個n內部整數值（對應於它們定義的位置）。例如，ROCK.ordinal()將返回0。