天文學助手Java菜單驅動程序與循環

Question

我試圖讓一個程序，讓用戶選擇一個行星，它會顯示有關該星球的特徵。

我想加入循環回菜單的能力，只要他們選擇了「5」來結束程序並且將選擇驗證爲1-5。

但是我有一些錯誤，我不知道如何擺脫。

import java.util.Scanner; 

public class AstronomyHelper 
{ 

    public static void main(String[] args) 
    { 

    //Declare a variable to hold the user's menu selection 
    int menuSelection; 

    //Declare a variable to hold the different planets 
    string Mercury, Venus, Earth, Mars; 


    //Create a scanner object for the keyboard input 
    Scanner keyboard = new Scanner(System.in); 


     do 
     { 
     //Display the menu and get the user's selection 
     displayMenu(menuSelection); 


     //Display the information for the user's selection 
     switch(menuSelection) 
     { 

      case 1: 
        System.out.println("\t\t\t\t\t\t\t\t\t\t MERCURY"); 
        System.out.println("_________________________________________________________"); 

        System.out.println("Average Distance from the sun: 57.9 million kilomenters"); 
        System.out.println("Mass: 3.31 x 10^23 kg"); 
        System.out.println("Surface Temperature: -173 to 430 degrees Celsius"); 

        break; 


      case 2: 
        System.out.println("\t\t\t\t\t\t\t\t\t\t VENUS"); 
        System.out.println("_________________________________________________________"); 

        System.out.println("Average Distance from the sun: 108.2 million kilometers"); 
        System.out.println("Mass: 4.87 x 10^24 kg"); 
        System.out.println("Surface Temperature: 472 degrees Celsius"); 

        break; 

      case 3: 
        System.out.println("\t\t\t\t\t\t\t\t\t\t EARTH"); 
        System.out.println("_________________________________________________________"); 

        System.out.println("Average Distance from the sun: 149.6 million kilometers"); 
        System.out.println("Mass: 5.967 x 10^24 kg"); 
        System.out.println("Surface Temperature: -50 to 50 degrees Celsius"); 

        break; 

      case 4: 
        System.out.println("\t\t\t\t\t\t\t\t\t\t MARS"); 
        System.out.println("_________________________________________________________"); 

        System.out.println("Average Distance from the sun: 227.9 million kiometers"); 
        System.out.println("Mass: 0.6424 x 10^24 kg"); 
        System.out.println("Surface Temperature: -140 to 20 degrees Celsius"); 

        break; 

     } 

     while(menuSelection !=5) 
     }  



     //Call the displayMenu method to display the menu options and get the user's selection 
     public displayMenu() 
     { 
     System.out.println("Please select a planet to view details about it's: "); 
     System.out.println("average distance from the sun, mass, and surface temperature."); 
     System.out.println("-------------------------------------------------------------"); 
     System.out.println("1. Mercury"); 
     System.out.println("2. Venus"); 
     System.out.println("3. Earth"); 
     System.out.println("4. Mars"); 
     System.out.println("5. EXIT the program"); 
     System.out.println("Enter your selection: "); 

     menuSelection = keyboard.nextInt(); 


      //Validate the menu selection 
      while (menuSelection < 1 || menuSelection > 5) 
      { 
       System.out.print("This is an invalid selection."); 
       System.out.print("Enter a selection from 1-5: "); 

       menuSelection = keyboard.nextInt(); 
      } 
      } 
} 

Answer 1

public displayMenu() // there must be a return type and int parameter 

如果你是在displayMenu訪問掃描儀對象（）方法，你必須聲明它們之外的main（）。

而且您也沒有正確關閉do-while循環。

Answer 2

聲明的鍵盤和menuSelection。正確關閉您的do-while並將回車聲明添加到displayMenu（）方法中。創建一個printPlanet（..）方法，以便您不需要複製/粘貼所有相同的數據。工作示例：

import java.util.Scanner; 

public class AstronomyHelper { 

public static void main(String[] args) { 
    int menuSelection = 0; 
    do { 
     // Display the menu and get the user's selection 
     menuSelection = displayMenu(); 
     // Display the information for the user's selection 
     switch (menuSelection) { 
     case 1: 
      printPlanet("MERCURY", "57.9", "3.31 x 10^23", "-173 to 430"); 
      break; 

     case 2: 
      printPlanet("VENUS", "108.2", "4.87 x 10^24", "472"); 
      break; 

     case 3: 
      printPlanet("EARTH", "149.6", "5.967 x 10^24", "-50 to 50"); 
      break; 

     case 4: 
      printPlanet("MARS", "227.9", "0.6424 x 10^24", "-140 to 20"); 
      break; 
     } 
    } 
    while (menuSelection != 5); 
} // Call the displayMenu method to display the menu options and get the 

// user's selection 
public static int displayMenu() { 
    System.out.println("Please select a planet to view details about it's: "); 
    System.out.println("average distance from the sun, mass, and surface temperature."); 
    System.out.println("_________________________________________________________"); 
    System.out.println("1. Mercury"); 
    System.out.println("2. Venus"); 
    System.out.println("3. Earth"); 
    System.out.println("4. Mars"); 
    System.out.println("5. EXIT the program"); 
    System.out.println("Enter your selection: "); 

    Scanner keyboard = new Scanner(System.in); 
    int menuSelection = keyboard.nextInt(); 

    // Validate the menu selection 
    while (menuSelection < 1 || menuSelection > 5) { 
     System.out.print("This is an invalid selection."); 
     System.out.print("Enter a selection from 1-5: "); 

     menuSelection = keyboard.nextInt(); 
    } 
    return menuSelection; 
} 
public static void printPlanet(String planet, String distanceToSun, String mass, String degrees) { 
    System.out.println("\t\t\t " + planet); 
    System.out.println("_________________________________________________________"); 
    System.out.println("Average Distance from the sun: " + distanceToSun + " million kiometers"); 
    System.out.println("Mass: " + mass + " kg"); 
    System.out.println("Surface Temperature: " + degrees + " degrees Celsius"); 
    System.out.println("_________________________________________________________"); 
} 
}