StringBuilder Class in Java

Constructors of StringBuilder in Java

Here's the table with a line added before it and the description in the table:

StringBuilder()

It constructs a string builder with no characters but an initial capacity of 16 characters by default.

StringBuilder object_name = new StringBuilder();

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StringBuilder(CharSequence seq)

CharSequence is an interface that provides read-only access to different types of character sequences. In simple words, it is a readable sequence of char values.
The constructor creates a string builder containing the same characters as the specified CharSequence.

StringBuilder object_name = new StringBuilder(“aabbcc”);

StringBuilder(int capacity)

It constructs a string builder with no characters but a specified capacity to hold characters.

StringBuilder object_name = new StringBuilder(10);

StringBuilder(String str)

It constructs a string builder initialized with the characters of the given string.
 

StringBuilder object_name = new StringBuilder(“hello”);

Methods of StringBuilder in Java

Also see, Hashcode Method in Java and Swap Function in Java

Java StringBuilder Examples

The insert() and append() methods, as mentioned before, perform the two main operations of inserting and appending characters to a given sequence. Let us see the methods of the StringBuilder class in action with the help of this example.

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

public class Main 
{
  public static void main(String[] args) throws Exception
  {
    StringBuilder str = new StringBuilder("ABC");

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

    str.append("D");
    System.out.println("\nAppending D => "+ str.toString());
    str.append("EFG",0,2);
    System.out.println("Appending EF => "+ str.toString());
    str.append(26);
    System.out.println("Appending 26 => "+ str.toString());

    System.out.println("\nCharacter at index 4 = "+ str.charAt(4));
    StringBuilder reverseStr = str.reverse();
    System.out.println("\nReverse String => "+ reverseStr.toString());

    str.insert(2,"GHI");
    System.out.println("\nInsertion => "+ str.toString());

    System.out.println("\nLength of the String => "+ str.length());

    System.out.println("\nSubString => "+ str.substring(2,6));

    str.replace(4,5,"G");
    System.out.println("\nReplacing I with G => "+ str.toString());

    System.out.println("\nIndex of G in the String = "+ str.indexOf("G"));
    System.out.println("Last index of G in the String = "+ str.lastIndexOf("G"));

    str.delete(4,6);
    System.out.println("\nAfter deleting \'GF\' from the String = "+ str.toString());

    str.appendCodePoint(48);
    System.out.println("\nAppending code point => "+ str);

    int capacity = str.capacity();
    System.out.println("\nCapacity of StringBuilder => "+ capacity);
  }
}

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Output:

String = ABC

Appending D => ABCD
Appending EF => ABCDEF
Appending 26 => ABCDEF26

Character at index 4 = E

Reverse String => 62FEDCBA

Insertion => 62GHIFEDCBA

Length of the String => 11

SubString => GHIF

Replacing I with G => 62GHGFEDCBA

Index of G in the String = 2
Last index of G in the String = 4

After deleting 'GF' from the String = 62GHEDCBA

Appending code point => 62GHEDCBA0

Capacity of StringBuilder => 19

Check out this problem - Longest Subarray With Sum K 

Must Read: Java System Out Println

Features of StringBuilder Class in Java

• The StringBuilder class is very much similar to the StringBuffer class, the only difference being that the former provides no guarantee of synchronization. Hence, it is used only by single threads.
   
• ‘Insert’ and ‘append’ are the principal methods of the StringBuilder class that are overloaded to accept values of any type.
   
• Every string builder has a character capacity that will create a new internal buffer to accommodate more characters upon exceeding.
   
• Passing a null value to StringBuilder’s constructors or methods results in NullPointerException.

Frequently Asked Questions

Why is StringBuilder mutable in Java?

StringBuilder is mutable to allow for modifications without creating new objects, enhancing performance during repetitive string manipulation tasks.

Why is StringBuilder faster?

StringBuilder is faster because it avoids the overhead of creating new string objects with each modification, reducing memory usage and processing time.

What are the benefits of StringBuilder in Java?

The benefits of StringBuilder in Java include improved performance for string manipulation, reduced memory overhead, and the ability to modify strings directly.

Conclusion 

String Manipulation is an important part of almost every application or program. Classes like String and StringBuilder enable programmers to deal with string values or data efficiently. This blog explains the StringBuilder class in Java and its features. It also lists the different functions and methods offered by the class and shows how to implement them.

Recommended problems:

• Find the Shortest Substring in a String
• Subsequence of a String
• Beautiful String
• Solid Principles in java

You can also check out our other blogs on Code360.