爲什麼我的代碼跳過if語句？

我發佈了一段較大的代碼段，我遇到了麻煩。它應該自行運行。爲了進行測試，只需在第一個提示處輸入一個即可。一旦它運行print語句，程序就會終止而不是詢問變量。我不明白爲什麼。有人能幫我嗎？爲什麼我的代碼跳過if語句？

import java.util.Scanner; 

public class Physics { 
    public static void main(String[] args) { 
    Scanner input = new Scanner(System.in); 

    int switchNumber; 
    String variableCaseOne; 
    double distance; 
    double initialVelocity; 
    double time; 
    double gravity; 

    System.out.println("This section is for projectile motion."); 
    System.out.println("Which equation would you like to use?"); 
    System.out.println("1. Horizontal Equation: D = Vi * t"); 
    System.out.println("2. Vertical Equation: D = Vi * t - (1/2)g * (t^2)"); 
    switchNumber = input.nextInt(); 
    if (switchNumber == 1) { 
     System.out.println("Tell me which variable you'd like to solve for."); 
     variableCaseOne = input.nextLine(); 
     if (variableCaseOne.equals("d")) { 
     System.out.println("Enter the Initial velocity."); 
     initialVelocity = input.nextDouble(); 
     System.out.println("Enter the time."); 
     time = input.nextDouble(); 
     System.out.println("Distance equals: " + initialVelocity * time); 
     } 

    } 
    } 
}

謝謝大家的幫助！

來源

2014-11-09 Matthew Crawford

可能重複http://stackoverflow.com/questions/7056749/scanner-issue-when- using-nextline-after-nextxxx） – PakkuDon 2014-11-09 00:49:36

主要的解決方案，如果我理解正確的嘗試：

if (switchNumber == 1) //the input is not a 1 the program will terminate

與交換機試試吧改變

variableCaseOne = input.nextLine（）;

至

variableCaseOne = input.next（）;

它爲我工作

SNPT

public static void main(String[] args) 
{ 
    Scanner input = new Scanner(System.in); 

    int switchNumber; 
    String variableCaseOne; 
    double initialVelocity; 
    double time; 

    System.out.println("This section is for projectile motion."); 
    System.out.println("Which equation would you like to use?"); 
    System.out.println("1. Horizontal Equation: D = Vi * t"); 
    System.out.println("2. Vertical Equation: D = Vi * t - (1/2)g * (t^2)"); 
    switchNumber = input.nextInt(); 
    if (switchNumber == 1) 
    { 
     System.out.println("Tell me which variable you'd like to solve for."); 
     variableCaseOne = input.next(); 
     if (variableCaseOne.equals("d")) 
     { 
      System.out.println("Enter the Initial velocity."); 
      initialVelocity = input.nextDouble(); 
      System.out.println("Enter the time."); 
      time = input.nextDouble(); 
      System.out.println("Distance equals: " + initialVelocity * time); 
     } 
    } 
    input.close(); 
}

[nextXXX後使用nextLine當掃描儀問題（指

來源

2014-11-09 01:05:51

如果這是你的解決方案，請投票支持=） – 2014-11-09 01:36:14

用戶需要15點聲望才能投票。 – mattias 2014-11-09 08:00:24

uppps耶對不起; P – 2014-11-09 16:31:54

當你在輸入1中輸入時，它是否也終止了程序？

當：

public static void main(String[] args) { 
    Scanner input = new Scanner(System.in); 

    int switchNumber; 
    String variableCaseOne; 
    double distance; 
    double initialVelocity; 
    double time; 
    double gravity; 

    System.out.println("This section is for projectile motion."); 
    System.out.println("Which equation would you like to use?"); 
    System.out.println("1. Horizontal Equation: D = Vi * t"); 
    System.out.println("2. Vertical Equation: D = Vi * t - (1/2)g * (t^2)");   

    switchNumber = input.nextInt(); 

    switch (switchNumber){ 

    case 1: System.out.println("Tell me which variable you'd like to solve for."); 
       variableCaseOne = input.next(); 

       if (variableCaseOne.equals("d")) { 
       System.out.println("Enter the Initial velocity."); 
       initialVelocity = input.nextDouble(); 
       System.out.println("Enter the time."); 
       time = input.nextDouble(); 
       System.out.println("Distance equals: " + initialVelocity * time); 
       } 

    case 2 : // your next case 
    }   
}

安德烈Bori的回答您的問題

來源

2014-11-09 00:54:30 Cronical

爲什麼我的代碼跳過if語句？

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