string buffer java program

import java.io.*;

public class stringBuffer{
public static void main(String[] args) throws Exception{
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
String str;
try{
System.out.print("Enter your name: ");
str = in.readLine();
str += ", This is the example of SringBuffer class and it's functions.";

//Create a object of StringBuffer class
StringBuffer strbuf = new StringBuffer();
System.out.print(strbuf.length());
strbuf.append(str);
System.out.println(strbuf);
strbuf.delete(0,str.length());

//append()
strbuf.append("Hello");
strbuf.append("World"); //print HelloWorld
System.out.println(strbuf);

//insert()
strbuf.insert(5,"_Java "); //print Hello_Java World
System.out.println(strbuf);

//reverse()
strbuf.reverse();
System.out.print("Reversed string : ");
System.out.println(strbuf); //print dlroW avaJ_olleH
strbuf.reverse();
System.out.println(strbuf); //print Hello_Java World

//setCharAt()
strbuf.setCharAt(5,' ');
System.out.println(strbuf); //prit Hello Java World

//charAt()
System.out.print("Character at 6th position : ");
System.out.println(strbuf.charAt(6)); //print J

//substring()
System.out.print("Substring from position 3 to 6 : ");
System.out.println(strbuf.substring(3,7)); //print lo J

//deleteCharAt()
strbuf.deleteCharAt(3);
System.out.println(strbuf); //print Helo java World

//capacity()
System.out.print("Capacity of StringBuffer object : ");
System.out.println(strbuf.capacity()); //print 21

//delete() and length()
strbuf.delete(6,strbuf.length());
System.out.println(strbuf); //no anything
}
catch(StringIndexOutOfBoundsException e){
System.out.println(e.getMessage());
}
}
}