Java StringBuffer class

 

Java StringBuffer class

StringBuffer is a peer class of String that provides much of the functionality of strings. String represents fixed-length, immutable character sequences while StringBuffer represents growable and writable character sequences.

Syntax:

StringBuffer s = new StringBuffer(“text");

Important Constructors of StringBuffer class:-

Constructor	Description
StringBuffer()	creates an empty string buffer with the initial capacity of 16.
StringBuffer(String str)	creates a string buffer with the specified string.
StringBuffer(int capacity)	creates an empty string buffer with the specified capacity as length.

 

Important methods of StringBuffer class

Modifier and Type	Method	Description
public synchronized StringBuffer	append(String s)	is used to append the specified string with this string. The append() method is overloaded like append(char), append(boolean), append(int), append(float), append(double) etc.
public synchronized StringBuffer	insert(int offset, String s)	is used to insert the specified string with this string at the specified position. The insert() method is overloaded like insert(int, char), insert(int, boolean), insert(int, int), insert(int, float), insert(int, double) etc.
public synchronized StringBuffer	replace(int startIndex, int endIndex, String str)	is used to replace the string from specified startIndex and endIndex.
public synchronized StringBuffer	delete(int startIndex, int endIndex)	is used to delete the string from specified startIndex and endIndex.
public synchronized StringBuffer	reverse()	is used to reverse the string.
public int	capacity()	is used to return the current capacity.
public void	ensureCapacity(int minimumCapacity)	is used to ensure the capacity at least equal to the given minimum.
public char	charAt(int index)	is used to return the character at the specified position.
public int	length()	is used to return the length of the string i.e. total number of characters.
public String	substring(int beginIndex)	is used to return the substring from the specified beginIndex.
public String	substring(int beginIndex, int endIndex)	is used to return the substring from the specified beginIndex and endIndex.

   What is mutable string:-

A string that can be modified or changed is known as mutable string. StringBuffer and StringBuilder classes are used for creating mutable string.

1) StringBuffer append() method

The append() method concatenates the given argument with this string.

class StringBufferExample

{  
public static void main(String args[])

{  
StringBuffer sb=new StringBuffer("Hello ");  
sb.append("Java");
System.out.println(sb);
}  
}  

 

2) StringBuffer insert() method

The insert() method inserts the given string with this string at the given position.

 

class StringBufferExample2

{  
public static void main(String args[])

{  
StringBuffer sb=new StringBuffer("Hello ");  
sb.insert(1,"Java");
System.out.println(sb);
}  
}  

3) StringBuffer replace() method

class StringBufferExample3

{  
public static void main(String args[])

{  
StringBuffer sb=new StringBuffer("Hello");  
sb.replace(1,3,"Java");  
System.out.println(sb); 
}  
} 

 4) StringBuffer delete() method

class StringBufferExample4

{  
public static void main(String args[])

{  
StringBuffer sb=new StringBuffer("Hello");  
sb.delete(1,3);  
System.out.println(sb);
}  
}