Explain all important methods of StringBuilder class?

StringBuilder is similar to StringBuffer in functionality but is not thread-safe, making it more efficient in single-threaded environments. It provides several methods to manipulate and modify strings efficiently. Here are some of the important methods in the StringBuilder class:

1. append(String str):

   • Appends the specified string str to the end of the current StringBuilder object.
   • Returns the modified StringBuilder object.

2. insert(int offset, String str):

   • Inserts the specified string str at the given offset position in the current StringBuilder object.
   • Returns the modified StringBuilder object.

3. delete(int start, int end):

   • Removes the characters from the start index (inclusive) to the end index (exclusive) from the current StringBuilder object.
   • Returns the modified StringBuilder object.

4. deleteCharAt(int index):

   • Removes the character at the specified index from the current StringBuilder object.
   • Returns the modified StringBuilder object.

5. replace(int start, int end, String str):

   • Replaces the characters from the start index (inclusive) to the end index (exclusive) with the specified string str.
   • Returns the modified StringBuilder object.

6. reverse():

   • Reverses the characters in the current StringBuilder object.
   • Returns the modified StringBuilder object.

7. substring(int start) and substring(int start, int end):

   • These methods are similar to the corresponding methods in the String class.
   • The first variant returns the substring starting from the start index to the end of the StringBuilder.
   • The second variant returns the substring from the start index (inclusive) to the end index (exclusive).

8. length():

   • Returns the length (number of characters) of the StringBuilder object.

9. capacity():

   • Returns the current capacity (size) of the StringBuilder object.

10. setLength(int newLength):

• • Sets the length of the StringBuilder to the specified newLength.
  • If newLength is greater than the current length, the StringBuilder will be padded with null characters ('\0') to reach the desired length.
  • If newLength is smaller than the current length, characters beyond the newLength will be truncated.

11. charAt(int index) and setCharAt(int index, char ch):

• • charAt(int index) returns the character at the specified index.
  • setCharAt(int index, char ch) sets the character at the specified index to the given ch.

These methods provide a wide range of string manipulation functionalities, making StringBuilder a powerful tool for building and modifying strings efficiently in Java. Remember that StringBuilder is mutable, so you can modify its contents and perform various string operations without creating multiple objects.