Problem in String Buffer - incrementing char in string

[Rahul Sudip Bose]

I want to take a char of a string,increment it and replace it with the incremented char. eg A should be B. I used replace method, insert method of StringBuffer and got BA instead of B. How do i rectify this problem ? Here is my code :

public class ChangeString
{
	public static void main(String args[ ])
	{
	  System.out.println("Inside main !");
	  StringBuffer sb = new StringBuffer("A"); 
	  System.out.println("sb is " + sb);
	  char c = sb.charAt(0);	  
	  c++;
	  String temp = Character.toString(c);
	  System.out.println("CHANGING CHAR !"); 	       
	  sb = sb.replace(0,0,temp);                                                     
	  System.out.println("sb is " + sb);
	}
}

Here is the incorrect output :

Inside main !
sb is A
CHANGING CHAR !
sb is BA

[Mohamed Sanaulla]

JavaDoc for replace() wrote:Replaces the characters in a substring of this sequence with characters in the specified String. The substring begins at the specified start and extends to the character at index end - 1 or to the end of

So you must change your End Index in replace() method

[Wouter Oet]

And you probably want a StringBuilder not a StringBuffer.

[Rahul Sudip Bose]

Mohamed Sanaulla wrote:

JavaDoc for replace() wrote:Replaces the characters in a substring of this sequence with characters in the specified String. The substring begins at the specified start and extends to the character at index end - 1 or to the end of

So you must change your End Index in replace() method

thank you, it worked. I thought that end and beginning should be the same because i only want to replace the first/zeroth char. So the method works like this : replace UP TO 'end index', NOT including end. Is that correct/complete ?

Can anyone suggest any other ways to do my program using StringBuffer only ?

[Mohamed Sanaulla]

Rahul Sudip Bose wrote:
Can anyone suggest any other ways to do my program using StringBuffer only ?

Using replace is a straight forward way.

[Campbell Ritchie]

Get the entire String as a char[] and use the ++ operator?

[Campbell Ritchie]

. . . and Wouter has already told you to use StringBuilder, not StringBuffer.

[Rahul Sudip Bose]

Campbell Ritchie wrote: . . . and Wouter has already told you to use StringBuilder, not StringBuffer.

This code will be used in threads, so i used StringBuffer...that brings another post....

[Wouter Oet]

In the code you've posted in your openings post it will only be used by one thread. If you've simplified the situation then it's good to inform us of that. For instance if you had mentioned in your openings post that the code is going to be used in a multithreaded environment then I wouldn't have made the suggestion for a StringBuilder.

[Campbell Ritchie]

Wouter Oet wrote: . . . if you had mentioned . . . that the code is going to be used in a multithreaded environment then I wouldn't have made the suggestion for a StringBuilder.

Nor would I.

[M Khalid]

Rahul Sudip Bose wrote:I want to take a char of a string,increment it and replace it with the incremented char. eg A should be B. I used replace method, insert method of StringBuffer and got BA instead of B. How do i rectify this problem ?    Here is my code :

public class ChangeString
{
	public static void main(String args[ ])
	{
	  System.out.println("Inside main !");
	  StringBuffer sb = new StringBuffer("A"); 
	  System.out.println("sb is " + sb);
	  char c = sb.charAt(0);	  
	  c++;
	  String temp = Character.toString(c);
	  System.out.println("CHANGING CHAR !"); 	       
	  sb = sb.replace(0,0,temp);                                                     
	  System.out.println("sb is " + sb);
	}
}

Here is the incorrect output :

Inside main !
sb is A
CHANGING CHAR !
sb is BA

Below is the corrected code - we can set the StringBuffer using setChatAt  method

import java.lang.*; // headers MUST be above the first class

public class ChangeString
{
    public static void main(String args[ ])
    {
      System.out.println("Inside main !");
      StringBuffer sb = new StringBuffer("A"); 
      System.out.println("sb is " + sb);
      char c = sb.charAt(0);      
      c++;
      System.out.println("CHANGING CHAR ! ");           
      sb.setCharAt(0 , c);                                              
      System.out.println("sb is " + sb);
    }
}

[M Khalid]

public class ChangeString
{
    public static void main(String args[ ])
    {
      System.out.println("Inside main !");
      StringBuffer sb = new StringBuffer("A"); 
      System.out.println("sb is " + sb);
      char c = sb.charAt(0);      
      c++;
      System.out.println("CHANGING CHAR ! "); 
      // We can use any of the following to increment and change a character in StringBuffer          
      //sb.setCharAt(0 , c);            // #1                  
      //sb.deleteCharAt(0).append(c);   // #2
      //sb.delete(0,1).append(c);       // #3                                    
      System.out.println("sb is " + sb);
    }
}

[Tony Docherty]

Please refrain from posting complete code solutions in the beginners forum. The aim of this form is to help people to solve their own problems not to give them complete code solutions. But because this thread is 6 years old I will leave your solution here this time.