StringBuffer Class In Java

Introduction

 A StringBuffer represents a string that can be modified. Whenever there is a concatenation operator (+) used with strings, a StringBuffer object is automatically created.

Constructors used of StringBuffer

Following constructors are used for StringBuffer class:

• public StringBuffer() Reserves room for 16 characters.
• public StringBuffer(int length) This sets the size of the buffer.
• public StringBuffer(String value) Accepts a String as an argument that sets the initial content and reserves room for 16 more characters without reallocation.

Methods Used with StringBuffer

The commonly used methods of the StringBuffer class are summarized:

• StringBuffer insert(String s)
  Inserts a string representation of boolean value at given position.
• int length()
  Determines length of StringBuffer object.
• void setCharAt(int pos, char ch):
  Sets the character at the position specified by pos with the new value specified by ch.
• String toString()
  Converts to string form.
• StringBuffer reverse()
  Reverses the characters within a SingleBuffer object.
• StringBuffer delete(int start, int end)
  This will delete a sequence of characters from the invoking object starting from position specified by start till the index -1 position specified by end.
• StringBuffer deleteCharAt(int pos)
  This will delete the character at the index specified by pos.
• StringBuffer replace(int start, int end, String s)
  It replaces one set of characters with another set. This replacement strings will replace from the position specified by start till the position specified by end.

Immutability

String in Java, once created, cannot be changed directly. This is called immutability in strings. To overcome this, Java provides the StringBuffer class, which represents a mutable sequence of characters. StringBuffer is a peer class of String and represents a growable and writable character sequence. These sequences may have characters inserted in the center or appended at the end. The concept of immutability is defined in the given example below:

Source Code

class StringBuf {
    protected StringBuf() {}
    public static void main(String args[]) {
        StringBuffer buf = new StringBuffer("Java");
        //appended
        buf.append(" Guide ver 1/");
        buf.append(3); // append Java Guide ver 1/3
        int index = 5;
        buf.insert(index, "Student "); // Set Java Student Guide Ver1/3
        index = 23;
        buf.setCharAt(index, '.');
        Set Java Student Guide Ver1 .3
        int start = 24;
        int end = 25;
        buf.replace(start, end, "4"); //replace Java Student Guide Ver 1.4
        String s = buf.toString(); //Convert to String
        System.out.println(s);
    }
}

Output

Summary

A StringBuffer represents a string that can be modified. StringBuffer insert(String s), StringBuffer reverse(), StringBuffer replace(int start, int end, String s), are a few of the functions used in the StringBuffer class. Java provides the StringBuffer class, which represents a mutable sequence of characters. StringBuffer is a peer class of String and represents growable and writable character sequence. These sequences may have characters inserted in the center or appended at the end.