StringBuffer char operation

In this chapter you will learn:

How to get a char from a certain index inside a StringBuffer
How copy part of a StringBuffer to a char array
How to update a char in a StringBuffer

Get a char from a certain index inside a StringBuffer

The value of a single character can be obtained from a StringBuffer via the charAt( ) method. char charAt(int index) returns the char value in this sequence at the specified index.

public class Main {
  public static void main(String[] argv) {
    StringBuffer sb = new StringBuffer();
    sb.append("java2s.com");
    //from ja v  a 2 s.com
    char ch =  sb.charAt(0);
    
    System.out.println(ch);

  }
}

The output:

Copy to a char array

void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin) copies characters from StringBuffer into the destination character array dst.

public class Main {
  public static void main(String args[]) {
    StringBuffer buffer = new StringBuffer("hello there");
/*ja v a2 s.co m*/
    System.out.printf("buffer = %s\n", buffer.toString());
    System.out.printf("Character at 0: %s\nCharacter at 4: %s\n\n", buffer.charAt(0), buffer
        .charAt(4));

    char charArray[] = new char[buffer.length()];
    buffer.getChars(0, buffer.length(), charArray, 0);
    System.out.print("The characters are: ");

  }
}

Update char in a StringBuffer

You can set the value of a character within a StringBuffer using setCharAt( ).

void setCharAt(int index, char ch) set character at the specified index is set to ch.

The following example demonstrates charAt( ) and setCharAt( ):

public class Main {
  public static void main(String args[]) {
    StringBuffer sb = new StringBuffer("java2s.com");
    System.out.println("buffer before = " + sb);
    System.out.println("charAt(1) before = " + sb.charAt(1));
//from  ja  v  a 2 s  .c o  m
    sb.setCharAt(1, 'i');
    sb.setLength(2);
    System.out.println("buffer after = " + sb);
    System.out.println("charAt(1) after = " + sb.charAt(1));

  }
}