The String Class

The String class defines the String object and the methods that can be applied to strings.  The class String includes methods for examining individual characters of the sequence, for comparing strings, for searching strings, for extracting substrings, and for creating a copy of a string with all characters translated to uppercase or to lowercase.  Specifications for this class and methods are located on the web http://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.html.  

Example:

                    String s = "abc";
                    String t = "def";

                    String f = "firetruck";

                    System.out.println ( s + t ) ;  // prints abcdef to the screen

                    System.out.println ( f.substring ( 0, 4 ) ); // prints fire to the screen

                    System.out.println ( f.substring (4) ); // prints truck to the screen

 

Common String Methods:

Method Result Description
charAt ( int i ) char Returns the character at position i of the string ( 0 based, ie. first character is position 0 ).
compareTo ( String t ) int Compares one string to another based on unicode values. Returns an integer value that will be 0, if both strings are the same.
concat ( String t ) String Adds (concatenates)  two strings together.
equals ( String t ) boolean Returns true when both strings are identical.
equalsIgnoreCase ( String t ) boolean Returns true when both strings are the same (ignoring case differences)
indexOf ( char c ) int Position of the first occurrence of character c in the string.
indexOf ( String t ) int Position of the first occurrence of string t in the string being checked.
length ( ) int Number of characters in the string.
replace ( char c, char d) String Returns the equivalent string, but with each occurrence of c replaced with d.
substring ( int i ) String Returns string starting at position i to the end of the string.
substring ( int i, int j ) String Returns string starting at position i up to but not including position j.
toLowerCase ( ) String Returns equivalent string in lower case.
toUpperCase ( ) String Returns equivalent string in upper case.
trim ( ) String Returns equivalent string with all leading and trailing white spaces removed.