String Class

• The String object is immutable.  Which means once the String object it is created, it cannot be changed.
• When you add two String objects together, a third object is created.
• String objects can be created by using the "new" keyword or by using a literal.  Example:
  1.  String strTest = new String("Hello")
  2.  String strTest = "Hello"

Note: The StringBuffer object allows strings to be concatenated without creating a new object.

Example

• System.out.println( "Hello".length() ); - shows 5
• String T = new String("Hello");
  System.out.println( T.length() );  - shows 5

• substring(begin, end*);  - warning, returns the begining char (index starts with 0) through (end - 1).

Examples

• "hello".substring(1,2) - returns "e"

• String's equals() is overridden to give you equality of the contents of the object.
• StringBuffer's equals just checks for equality of the object references.  Note:   Object's equals() is not overridden.

Example:
String strExample = "Hello World"
if ( strExample.equalsIgnoreCase("Hello World") { etc...}

Example:
String strExample = "Hello World"
if ( strExample.equalsIgnoreCase("hello world") { etc...}

String strExNull;
strExNull = null;
if ( strExNull != null ) {} etc...
 

"\\d{5}" - any digit, exactly 5 times.  Good for zip codes.