OOP(lesson1&2)

• Strings


  Used for storing text-based data in programming

  
• String class


  Immutable and non-primitive data type used to store the characters of the sequence

  
• Ways to compare strings in Java

  • Equality operator ==
  • equals() method
  • compareTo() method

  
• Equality operator ==


  Compares two strings
• The == operator does not work when comparing two string objects</b>
• equals() method


  Compares the original content of the string

  
• equalsIgnoreCase() method


  Compares two strings, ignoring case
• compareTo() method


  Compares two strings lexicographically and returns an integer value

  
• endsWith() method


  Checks whether the given string ends with the specified string suffix
• startsWith() method


  Checks whether the given string starts with the specified string prefix
• regionMatches() method


  Tests if two string regions are matching or equal
• Immutability is the biggest problem of Java String if not used correctly
• Mutable string


  A string that can be modified or changed
• StringBuffer


  A mutable sequence of characters
• StringBuffer


  • Mutable, initial capacity can be specified, append() method to add characters, insert() method to insert characters, delete() method to remove characters, reverse() method to reverse the order of characters
• StringBuffer constructors


  StringBuffer(), StringBuffer(String str), StringBuffer(int capacity)
• StringBuilder


  A mutable sequence of characters, differs from StringBuffer in terms of synchronization
• Where possible, it is recommended to use StringBuilder in preference to StringBuffer as it will be faster under most implementations
• Instances of StringBuilder are not safe for use by multiple threads
• If synchronization is required, it is recommended to use StringBuffer
• StringBuilder constructors


  StringBuilder(), StringBuilder(String str), StringBuilder(int length)
• Differences between String, StringBuffer, and StringBuilder


  • String is immutable, StringBuffer is synchronized, StringBuilder is not synchronized
  • Concatenation operator "+" is internally implemented using either StringBuffer or StringBuilder
  • Use String if you require immutability, use StringBuffer if you need mutable + thread-safety, use StringBuilder if you require mutable + without thread-safety