String Buffer Class

String buffer objects are used to store character sequences but they are mutable objects which means that they can be altered directly.

Creating a String Buffer Object:-
StringBuffer s1 = null;
StringBuffer s2 = new StringBuffer();
StringBuffer s3 = new StringBuffer("JAVA");
StringBuffer s4 = new StringBuffer(1000);     // Size of string buffer is 1000

By default initial memory allocated to s2 is 16 characters.
For s3 it is 4+16 characters.
So when we create a StringBuffer object, by default memory is allocated for 16 characters. When we create a StringBuffer object and initialize it with string. Then memory allocated will be length of string and 16 characters more. We can also create object with specified memory.

StringBuffer s3 = new StringBuffer("JAVA");
System.out.println(s3.capacity);                // 4 + 16
System.out.println(s3.length);                    // 4

The capacity of StringBuffer object is no of characters it can hold at any instant and length is the number of character it is holding.