不區分大小寫用於選擇案例驗證

Question

我試圖讓我的元素字符串變量的用戶輸入，以便它不區分大小寫。下的變量部分我簡單試圖

字符串element.equalsIgnoreCase

在我INPUT部我試圖

element.toLowerCase = keyboard.nextLine（）;

這些都沒有工作。我嘗試翻轉他們，並得到錯誤。在RESULTS部分中，我嘗試在第二個if語句內部的元素上粘貼這些元素並獲得錯誤。這讓我想到了第二個問題，我需要它對距離（if語句正常工作）以及元素進行輸入驗證，以便區分大小寫。

基本上，如果用戶輸入「AiR」或「AIR」等我需要選擇的情況下運行，但如果他們輸入一些愚蠢的像「鴨子」我需要它產生其他消息「請輸入空氣，水或鋼「

此外，我在我的if語句有困難，因爲我不知道如何使它運行，如果只有三個單詞中的一個（不區分大小寫）輸入。我嘗試設置它，以便如果（元素==「空氣」||「水」||「鋼」），但似乎沒有工作。之前有人標記此：我花了半個小時搜索堆棧和其他網站沒有找到我所需要的運氣。我看到了一些關於在不同的環境下對不區分大小寫的情況，但沒有幫助。我嘗試過這個。我需要這對於驗證而言不區分大小寫，而不是輸出。

//finds the scanner class in the Java library to make it available to this program 
import java.util.Scanner; 

//Defines the class name, must match txt file name 
public class SpeedOfSound 
{ 
    public static void main(String[] args) 
    { 

    /* ~~~~~~~~~~~~~~~~~~~(VARIABLES)~~~~~~~~~~~~~~~~~~~*/ 

     String element.equalsIgnoreCase; //String variable to store user-defined name 
     double distance; //double variable to store user-defined distance 
     double time; //double variable to store final time result 
     final double AIR = 1100; //constant double variable to store the time it takes sound to travel through air 
     final double WATER = 4900; //constant double variable to store the time it takes sound to travel through water 
     final double STEEL = 16400; //constant double variable to store the time it takes sound to travel through steel 

    /* ~~~~~~~~~~~~~~~~~~~(INPUT)~~~~~~~~~~~~~~~~~~~*/ 

//Creates a new scanner to allow user to enter input 
     Scanner keyboard = new Scanner(System.in); 

//Prompts the user to input air, water or steel 
     System.out.print("Enter one of the following: Air, Water or Steel: "); 
     element.toLowerCase = keyboard.nextLine(); 

//Prompts the user to input a distance 
     System.out.print("How far will the sound wave travel? "); 
     distance = keyboard.nextInt(); 

    /* ~~~~~~~~~~~~~~~~~~~(RESULTS)~~~~~~~~~~~~~~~~~~~*/ 

    if (distance >= 0 && distance <= 10000) 
    { 
     if (element == "Air"||"Water"||"Steel") 
     { 

     switch (element) 
     { 
      case "Air": 
      System.out.print("AirTest"); 
      break; 

      case "Water": 
      System.out.print("WaterTest"); 
      break; 

      case "Steel": 
      System.out.print("SteelTest"); 
      break; 
     } 

     } 

    else 
    { 
     System.out.print("Distance entered needs to be a number between 0 and 10000"); 
    } 
    } 
    else 
    { 
     System.out.print("Please enter Air, Water or Steel"); 
    } 


//END 
    } 
} 

Answer 1

首先，調用輸入與toLowerCase（），然後將其保存爲小寫。另外，你需要用a.equals（B），而不是一個== b鍵比較字符串：

//finds the scanner class in the Java library to make it available to this program 
import java.util.Scanner; 

//Defines the class name, must match txt file name 
public class SpeedOfSound 
{ 
    public static void main(String[] args) 
    { 

    /* ~~~~~~~~~~~~~~~~~~~(VARIABLES)~~~~~~~~~~~~~~~~~~~*/ 

     String element; //String variable to store user-defined name 
     double distance; //double variable to store user-defined distance 
     double time; //double variable to store final time result 
     final double AIR = 1100; //constant double variable to store the time it takes sound to travel through air 
     final double WATER = 4900; //constant double variable to store the time it takes sound to travel through water 
     final double STEEL = 16400; //constant double variable to store the time it takes sound to travel through steel 

    /* ~~~~~~~~~~~~~~~~~~~(INPUT)~~~~~~~~~~~~~~~~~~~*/ 

//Creates a new scanner to allow user to enter input 
     Scanner keyboard = new Scanner(System.in); 

//Prompts the user to input air, water or steel 
     System.out.print("Enter one of the following: Air, Water or Steel: "); 
     element = keyboard.nextLine().toLowerCase(); 

//Prompts the user to input a distance 
     System.out.print("How far will the sound wave travel? "); 
     distance = keyboard.nextInt(); 

    /* ~~~~~~~~~~~~~~~~~~~(RESULTS)~~~~~~~~~~~~~~~~~~~*/ 

    if (distance >= 0 && distance <= 10000) 
    { 
     if (element.equals("air")|| 
      element.equals("water")|| 
      element.equals("steel")) 
     { 

     switch (element) 
     { 
      case "air": 
      System.out.print("AirTest"); 
      break; 

      case "water": 
      System.out.print("WaterTest"); 
      break; 

      case "steel": 
      System.out.print("SteelTest"); 
      break; 
     } 

     } 

    else 
    { 
     System.out.print("Distance entered needs to be a number between 0 and 10000"); 
    } 
    } 
    else 
    { 
     System.out.print("Please enter Air, Water or Steel"); 
    } 


//END 
    } 
} 

Answer 2

element.toLowerCase = keyboard.nextLine();不是一個有效的建設。嘗試使用element = keyboard.nextLine().toLowerCase();

另請注意，String element.equalsIgnoreCase;和element == "Air"||"Water"||"Steel"也無效。我會建議閱讀一些java tutorial。

關於你最初的問題，你應該堅持一個if建設和String#equalsIgnoreCase()：

if (element.equalsIgnoreCase("Air")) { 
    // something 
} else if (element.equalsIgnoreCase("Water")) { 
    // something else 
} 
// etc