如何獲得位於前另一個字符

Question

例如一個角色，我有

Scanner scan = new Scanner(System.in); 
String a = scan.nextLine(); 

讓我們假設一個用戶輸入abctd。

getCharcterBeforeT(example) - 在這部分需要幫助

Answer 1

怎麼是這樣的：

import java.util.Scanner; 

class Main { 
    public static void main(String[] args) { 
    Scanner scan = new Scanner(System.in); 
    System.out.print("Enter a string:"); 
    String intialString = scan.nextLine(); 
    System.out.print("What is the character you would like to get the character before:"); 
    String character = ""; 
    while(true){ 
     character = scan.nextLine(); 
     if(character.length()==1) 
     break; 
     else 
     System.out.print("Please enter only 1 character:"); 
    } 
    System.out.println(getCharcterBeforeT(intialString, character.charAt(0))); 
    } 

    public static char getCharcterBeforeT(String str, char c){ 
    char returnChar = ' '; 
    if (str.indexOf(c) == -1){ 
     System.out.println("Character '" + c + "' not found"); 
    } else if (str.indexOf(c) == 0){ 
     System.out.println("Character '" + c + "' is at start of string"); 
    } else { 
     returnChar = str.charAt(str.indexOf(c) - 1); 
    } 
    return returnChar; 
    } 
} 

控制檯：

Enter a string: abctd 
What is the character you would like to get the character before: a 
Character 'a' is at start of string 

Enter a string: abctd 
What is the character you would like to get the character before: b 
a 

Enter a string: abctd 
What is the character you would like to get the character before: q 
Character 'q' not found 

試試吧here!