如何從Integer ArrayList中返回平均值而封閉開關

Question

我正在嘗試編寫一個腳本來記錄保齡球分數以及部分使用Java集合框架來彙總存儲的記錄。

這是一項正在進行的工作，但我至今是：

package mod6; 
import java.util.*; 
import java.lang.*; 
import java.io.*; 
import java.math.*; 
//import org.apache.commons.math3.stat.descriptive.DescriptiveStatistics; 

/** 
* @author Jason 
*Use the collections framework and generic types to create a bowling score tracker collection. 
*Design a data structure that will be used as elements in a collection. 
*Each element should contain a unique name of the bowler and a list of scores and dates of the games they have played. 

Then print to the screen each: 

    Bowler name 
    Number of games 
    Average score of all of the games 
    Score of their last game 
    Date of their last game 

*/ 



public class Bowling { 
    // Function from StackOverflow to get mean 
    private static double calculateAverage(List <Integer> marks) { 
      Integer sum = 0; 
      if(!marks.isEmpty()) { 
      for (Integer mark : marks) { 
       sum += mark; 
      } 
      return sum.doubleValue()/marks.size(); 
      } 
      return sum; 
     } 

      public static void main(String[] args) throws IOException { 
       BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in), 1); 

       // Local variables 
       int swValue; 
       int gameUID = 1; 

       do{ 
       // Display menu graphics 
       System.out.println("============================"); 
       System.out.println("| BOWLING SCORE TRACKER |"); 
       System.out.println("============================"); 
       System.out.println("| Options:     |"); 
       System.out.println("|  1. Enter a Game |"); 
       System.out.println("|  2. Summarize Games|"); 
       System.out.println("|  3. Exit   |"); 
       System.out.println("============================"); 
       swValue = Keyin.inInt(" Select option: "); 
       ArrayList<String> names = new ArrayList<String>(); // Use Java Collections Framework for bowling player names 
       ArrayList<Integer> uid = new ArrayList<Integer>(); // Use Java Collections Framework for bowling game UID 
       ArrayList<Integer> scores=new ArrayList<Integer>(); // Use Java Collections Framework for bowling game scores 

       // Switch construct 
       switch (swValue) { 
       case 1:            // Accept user input to record a game 
        System.out.println("Let's add a game!"); 


        // Add game ID 
        uid.add(gameUID); 
        gameUID++;           // Increment the bowling game UID to prepare for additional game records 

        // Add names 
        System.out.println(""); 
        System.out.println("Please Bowler 1's name then press ENTER"); 
        String a = stdin.readLine();      // get a line of user input as a String player name 
        names.add(a);          // add it to the names collection/ArrayList 
        System.out.println("Please Bowler 2's name then press ENTER"); 
        String b = stdin.readLine();      // get a line of user input as a String player name 
        names.add(b);          // add it to the names collection/ArrayList 

        // Add scores 
        System.out.println("Please Bowler 1's score then press ENTER"); 
        Scanner in = new Scanner(System.in); 
        int num = in.nextInt();        // get a line of user input for player's score 
        scores.add(num);         // add it to the names collection/ArrayList 

        System.out.println("Please Bowler 2's score then press ENTER"); 
         num = in.nextInt();        // get a line of user input for player's score 
        scores.add(num);         // add it to the names collection/ArrayList 

        // Print Game UID 
        System.out.println("Game ID:" + (gameUID - 1)); // The - 1 is because I incremented gameUID already 
        // Print players' names 
        names.stream().forEach((string) -> { 
         System.out.println("Player: " + string); 
        }); 

        // Print players' scores 
        scores.stream().forEach((int1) -> { 
         System.out.println("Player Score: " + int1); 
        }); 
        break; 
       case 2: 
        System.out.println("Allow me to summarize your game(s):"); 
        System.out.println("The average score from all of your games is:"); 
        double mean = calculateAverage(scores); 
        System.out.print(mean); 
        System.out.println(""); 
        break; 
       case 3: 
        System.out.println("Exit selected"); 
        break; 
       default: 
        System.out.println("Invalid selection"); 
       } 
     }    while(swValue != 3); 
    } 
} 

//********************************************************** 
//********************************************************** 
//Program: Keyin 
//Citation: I got this from 
//http://www.java2s.com/Code/Java/Development-Class/Javaprogramtodemonstratemenuselection.htm 
//Topics: 
//1. Using the read() method of the ImputStream class 
// in the java.io package 
//2. Developing a class for performing basic console 
// input of character and numeric types 
//********************************************************** 
//********************************************************** 
class Keyin { 

//******************************* 
// support methods 
//******************************* 
//Method to display the user's prompt string 
public static void printPrompt(String prompt) { 
    System.out.print(prompt + " "); 
    System.out.flush(); 
} 

//Method to make sure no data is available in the 
//input stream 
public static void inputFlush() { 
    int dummy; 
    int bAvail; 

    try { 
    while ((System.in.available()) != 0) 
     dummy = System.in.read(); 
    } catch (java.io.IOException e) { 
    System.out.println("Input error"); 
    } 
} 

//******************************** 
// data input methods for 
//string, int, char, and double 
//******************************** 
public static String inString(String prompt) { 
    inputFlush(); 
    printPrompt(prompt); 
    return inString(); 
} 

public static String inString() { 
    int aChar; 
    String s = ""; 
    boolean finished = false; 

    while (!finished) { 
    try { 
     aChar = System.in.read(); 
     if (aChar < 0 || (char) aChar == '\n') 
     finished = true; 
     else if ((char) aChar != '\r') 
     s = s + (char) aChar; // Enter into string 
    } 

    catch (java.io.IOException e) { 
     System.out.println("Input error"); 
     finished = true; 
    } 
    } 
    return s; 
} 

public static int inInt(String prompt) { 
    while (true) { 
    inputFlush(); 
    printPrompt(prompt); 
    try { 
     return Integer.valueOf(inString().trim()).intValue(); 
    } 

    catch (NumberFormatException e) { 
     System.out.println("Invalid input. Not an integer"); 
    } 
    } 
} 

public static char inChar(String prompt) { 
    int aChar = 0; 

    inputFlush(); 
    printPrompt(prompt); 

    try { 
    aChar = System.in.read(); 
    } 

    catch (java.io.IOException e) { 
    System.out.println("Input error"); 
    } 
    inputFlush(); 
    return (char) aChar; 
} 

public static double inDouble(String prompt) { 
    while (true) { 
    inputFlush(); 
    printPrompt(prompt); 
    try { 
     return Double.valueOf(inString().trim()).doubleValue(); 
    } 

    catch (NumberFormatException e) { 
     System.out 
      .println("Invalid input. Not a floating point number"); 
    } 
    } 
} 
} 

結果是：

============================ 
| BOWLING SCORE TRACKER | 
============================ 
| Options:     | 
|  1. Enter a Game | 
|  2. Summarize Games| 
|  3. Exit   | 
============================ 
Select option: 1 
Let's add a game! 

Please Bowler 1's name then press ENTER 
Marky 
Please Bowler 2's name then press ENTER 
Mark 
Please Bowler 1's score then press ENTER 
10 
Please Bowler 2's score then press ENTER 
20 
Game ID:1 
Player: Marky 
Player: Mark 
Player Score: 10 
Player Score: 20 
============================ 
| BOWLING SCORE TRACKER | 
============================ 
| Options:     | 
|  1. Enter a Game | 
|  2. Summarize Games| 
|  3. Exit   | 
============================ 
Select option: 2 
Allow me to summarize your game(s): 
The average score from all of your games is: 
0.0 
============================ 
| BOWLING SCORE TRACKER | 
============================ 
| Options:     | 
|  1. Enter a Game | 
|  2. Summarize Games| 
|  3. Exit   | 
============================ 
Select option: 3 
Exit selected 

而我去的結果是：

============================ 
| BOWLING SCORE TRACKER | 
============================ 
| Options:     | 
|  1. Enter a Game | 
|  2. Summarize Games| 
|  3. Exit   | 
============================ 
Select option: 1 
Let's add a game! 

Please Bowler 1's name then press ENTER 
Marky 
Please Bowler 2's name then press ENTER 
Mark 
Please Bowler 1's score then press ENTER 
10 
Please Bowler 2's score then press ENTER 
20 
Game ID:1 
Player: Marky 
Player: Mark 
Player Score: 10 
Player Score: 20 
============================ 
| BOWLING SCORE TRACKER | 
============================ 
| Options:     | 
|  1. Enter a Game | 
|  2. Summarize Games| 
|  3. Exit   | 
============================ 
Select option: 2 
Allow me to summarize your game(s): 
The average score from all of your games is: 
**15.0** 
============================ 
| BOWLING SCORE TRACKER | 
============================ 
| Options:     | 
|  1. Enter a Game | 
|  2. Summarize Games| 
|  3. Exit   | 
============================ 
Select option: 3 
Exit selected 

Answer 1

你必須把這條線

ArrayList<Integer> scores=new ArrayList<Integer>(); 

外面你做的，而循環

ArrayList<Integer> scores=new ArrayList<Integer>(); 
    do{ 

    // Switch and so on 

    }while (test); 

因爲你在每個循環重新初始化並刪除之前的值