The StringBuffer Class

Since String objects are immutable, you cannot manipulate the characters of an instantiated String. If you need to do this, use a java.lang.StringBuffer instead:

      // Create a string buffer from a string

      StringBuffer b = new StringBuffer("Mow");

      // Get and set individual characters of the StringBuffer

      char c1 = b.charAt(0); // Returns 'M': just like String.charAt()

      b.setCharAt(0, 'N'); // b holds "Now": can't do that with a String!

      // Append to a StringBuffer

      b.append(' '); // Append a character

      b.append("is the time."); // Append a string

      b.append(23); // Append an integer or any other value

      // Insert Strings or other values into a StringBuffer

      b.insert(6, "n't"); // b now holds: "Now isn't the time.23"

      // Replace a range of characters with a string (Java 1.2 and later)

      b.replace(4, 9, "is"); // Back to "Now is the time.23"

      // Delete characters

      b.delete(16, 18); // Delete a range: "Now is the time"

      b.deleteCharAt(2); // Delete 2nd character: "No is the time"

      b.setLength(5); // Truncate by setting the length: "No is"

      // Other useful operations

      b.reverse(); // Reverse characters: "si oN"

      String s11 = b.toString(); // Convert back to an immutable string

      s11 = b.substring(1,2); // Or take a substring: "i"

      b.setLength(0); // Erase buffer; now it is ready for reuse