StringBuilder Class In Java with Examples

StringBuilder Java  In Java: In our last post, we have discussed the StringBuffer, and in this post, we are going to discuss the StringBuilder class, which is also like string class objects. the only difference between a String object and StringBuilder objects is string objects are immutable where the StringBuilder objects are mutable, which means these can be modifiable.

Another main difference between StringBuffer and StringBuilder is Sting buffer are Synchronized in nature, whereas the StringBuilder objects are not synchronized, which means StringBuilder objects are not thread-safe. This class is designed as a replacement for StringBuffer because the performance of StringBuffer is slower as compare to the StringBuilder because of the synchronization.

StringBuilder Class Constructors

StringBuilder(): Constructs a string builder with no characters in it and an initial capacity of 16 characters.
StringBuilder(int capacity): Constructs a string builder with no characters in it and an initial capacity specified by the capacity argument.
StringBuilder(CharSequence seq): Constructs a string builder that contains the same characters as the specified CharSequence.
StringBuilder(String str): Constructs a string builder initialized to the contents of the specified string.

import java.util.*;
import java.util.concurrent.LinkedBlockingQueue;

public class Stringbuilderex 
{
   public static void main(String[] argv) throws Exception
   {
      // create a StringBuilder object
      // usind StringBuilder() constructor
      StringBuilder str = new StringBuilder();
      str.append("StringBuilder");

      // print string
      System.out.println("String = "+ str.toString());

      // create a StringBuilder object
      // usind StringBuilder(CharSequence) constructor
      StringBuilder str1 = new StringBuilder("AAAABBBCCCC");

      // print string
      System.out.println("String1 = "+ str1.toString());

      // create a StringBuilder object
      // usind StringBuilder(capacity) constructor
      StringBuilder str2 = new StringBuilder(10);

      // print string
      System.out.println("String2 capacity = " + str2.capacity());

      // create a StringBuilder object
      // usind StringBuilder(String) constructor
      StringBuilder str3 = new StringBuilder(str1);

      // print string
      System.out.println("String3 = " + str3.toString());
   }
}

StringBuilder Methods

append(): This method attaches the passed string at the end of the exiting string.

package com.journaldev.java;
public class StringBuilderExample 
{
   public static void main(String[] args) 
   {
      StringBuilder sb = new StringBuilder("Hello ");
      // now original string is changed
      sb.append("World");
      // prints Hello World
      System.out.println(sb);
   }
}

Insert(): This method helps you to insert a character sequence or work at a given index.

StringBuilder sb = new StringBuilder("HellWorld");
sb.insert(4, "o ");
//prints Hello World
System.out.println(sb);