String

Review of String (1) String is a user-defined class that is created by the programmers who implemented the Java library

Review of String (2)  Defining String variables (object definition syntax): The Java compiler recognize a short hand notation for String creation:

How a String object is stored A String is an object:

Instance methods on String (1) The general format to use an operation on a String object:

Instance methods on String (2) length(): returns the length of the string charAt(n): returns the charcater at position n in the string

Instance methods on String (3) substring(i,j): returns the substring from position i up to (not including) position j of the string Concatenating strings:

Comparison operations The == operator in Java always compare whether the value  stored in variables are equal. The test x == y does not test whether the strings stored in x and y are equal to one another

Comparing if strings are equal based on their content (1) The instance method used to compare equality of two strings s1 and s2 based on their content:

Comparing if strings are equal based on their content (2) The instance method used to compare equality of two strings s1 and s2 without considering upper/lower case difference:

Ranking 2 strings (1) The instance method used to rank of two strings s1 and s2  in alpha-numerical order:

Ranking 2 strings (2) The instance method used to rank of two strings s1 and s2  without considering upper/lower case in alpha- numerical order:

Finding substrings (1) Finding (locate) the first occurrence of a substring sub in a string s:

Finding substrings (2) The instance method used to find (locate) the last occurrence of a substring sub in a string s is:

Transformation Operations (1) Transform all upper case letters in a string s into lower case letters Transform all lower case letters in a string s into upper case letters

Transformation Operations (2) Replace the first occurrence of a substring old inside a string s by the substring new replace all occurrences of a substring old inside a string s by the substring new

Strings in Java are immutable The instance methods in the String class do not change  the implicit parameter (the string)

String and Array (1) a String is a single object an array of char are a series (multiple) of variables Converts a string into an array of char:

String and Array (2) convert an array of char into a String object, we use a constructor method in the String class:

String and Array (3) The chances are very good that the Java library contains  instance methods that help you write your program