字符追加在字符串在運行時錯誤變量可能尚未初始化

Question

對於實例我有一個錯誤，如果想要打印輸出for循環結束後cipher字符串：

System.out.print("Cipher Text IS : >>> "); 
for (int i = 0; i < len; i++) 
{ 
    char a = plainText.charAt(i); 
    for (int j = 0; j < allChar.length(); j++) 
    { 
     if (allChar.charAt(j) == a) 
     { 
      char c = allChar.charAt(j + key); 
      String cipher = "null" + c; 

      System.out.print("\t" + c); 
     } 
     System.out.println(cipher); 
    } 
} 

Answer 1

您需要更改這個（見我的評論在線）：

for(int j=0; j<allChar.length(); j++) 
{ 
    if(allChar.charAt(j) == a)     
    { 
     char c= allChar.charAt(j+key); 
     String cipher = "null"+c; 

     System.out.print("\t"+c); 
    } 
    System.out.println(cipher); 
    // cipher is not defined/initialzed here. 
    // this is not the "end" of the loop but within its body, 
    // thus prints on every iteration 
} 

到：

cipher = ""; // initalize cipher 
for(int j = 0; j < allChar.length(); j++) 
{ 
    if(allChar.charAt(j) == a)     
    { 
     char c= allChar.charAt(j + key); 
     cipher += "null"+c; // don't know the logic here! 

     System.out.print("\t" + c); 
    } 
} 
System.out.println(cipher); // print result after loop 

Answer 2

銀行經營ing代碼ATBASH密碼感謝幫助Dears

import java.util.Scanner; 

    class Asif 
    { 
     public static void main(String args[]) 
     { 
     String allchar = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; 
     Scanner a= new Scanner(System.in); 
     System.out.println("Enter the plainText For Cipher here "); 
     String plainText=a.nextLine(); 
     plainText=plainText.replaceAll(" ", ""); 
     plainText=plainText.toUpperCase(); 
     int len= plainText.length(); 
     int len1 = allchar.length(); 
     String cipher=""; 

     for(int i=0; i<len; i++) 
     { 
      char b=plainText.charAt(i); 
      for(int j=0; j<26; j++) 
      { 
       char c=allchar.charAt(j); 
       if(c == b) 
       { 
        int index=allchar.indexOf(c); 
      int position=25-index; 
        cipher+= allchar.charAt(position); 
        break; 

       } 
      } 
     } 
     System.out.println(cipher);  
    } 
}