StringBuffer and its methods with example

StringBuffer

StringBuffer is a peer class of String that provides much of the functionality of strings.
String represents fixed-length, immutable character sequences.
StringBuffer represents growable and writable character sequences.
StringBuffer may have characters and substrings inserted in the middle or appended to the end.
It will automatically grow to make room for such additions and often has more characters preallocated than are actually needed, to allow room for growth.

StringBuffer Constructors

StringBuffer s=new StringBuffer();

StringBuffer(int size)It accepts an integer argument that explicitly sets the size of the buffer.
Example:

StringBuffer s=new StringBuffer(20);

StringBuffer(String str): It accepts a String argument that sets the initial contents of the StringBuffer object and reserves room for 16 more characters without reallocation.
Example:

StringBuffer s=new StringBuffer("Sarthak");

Methods

length( ) and capacity( ): The length of a StringBuffer can be found by the length( ) method, while the total allocated capacity can be found by the capacity( ) method.
Example:

int p = s.length();
int q = s.capacity();
System.out.println("Length of string"+ p);
System.out.println("Capacity of string" + q);

append( ): It is used to add text at the end of the existence text. Here are a few of its forms:
Example:

StringBuffer s = new StringBuffer("Sarthak");
s.append(" Patel");

insert( ): It is used to insert text at the specified index position. These are a few of its forms.
StringBuffer insert(int index, String str)
Example:

StringBuffer s = new StringBuffer("Sarthak");
s.insert(5, "for");

StringBuffer s = new StringBuffer("Sarthak");
s.insert(0, 5);

reverse( ): It can reverse the characters within a StringBuffer object using reverse( ).This method returns the reversed object on which it was called.
Example:

StringBuffer s = new StringBuffer("Sarthak");
s.reverse();

delete( ) and deleteCharAt( ): It can delete characters within a StringBuffer by using the methods delete( ) and deleteCharAt( ). The delete( ) method deletes a sequence of characters from the invoking object.The deleteCharAt( ) method deletes the character at the index specified by loc.
StringBuffer delete(int startIndex, int endIndex)
Example:

StringBuffer s = new StringBuffer("Sarthak Patel");
s.delete(0, 5);

StringBuffer s = new StringBuffer("Sarthak Patel");
s.deleteCharAt(7);

replace( ): It can replace one set of characters with another set inside a StringBuffer object by calling replace( ).
StringBuffer replace(int startIndex, int endIndex, String str)
Example:

StringBuffer s = new StringBuffer("Sarthak Patel");
s.replace(5, 8, "are");