String class:

• The “String” class provides a number of methods that examines for a string inside of a string.
• The term “substring” refers to a string that denotes another string’s part.
• The “startsWith” method would determine whether calling string of object begins with a particular substring.
  • The method returns “true” if string begins with specified substring, it returns “false” otherwise.
• The “endsWith” method would determine whether calling string would end with a specified substring.
  • The method returns “true” if string ends with specified substring, it returns “false” otherwise.
• The “regionMatches” method would determine whether specified regions for two strings match.
  • The first argument of this method can be “true” or “false” that indicates whether a case-insensitive comparison could be performed.

StringBuilder class:

• The “StringBuilder” class is same as “String” class except that contents of “StringBuilder” objects could be changed.
• It provides several methods that “String” class does not have.
• The “append” method accepts an argument that might be a primitive data type.
  • It appends a string representation to contents of calling object.
• The “insert” method accepts two arguments, an integer that specifies position in string of calling object as well as value to be inserted.
• The “replace” method replaces the occurrences of one character with another character.
• The “toString” method converts a “StringBuilder” object in to a regular string.