Regex 101 - Introduction

Predefined Character Classes

. Any character (may or may not match line terminators)

\d A digit: [0-9]

\D A non-digit: [^0-9]

\s A whitespace character: [ \t\n\x0B\f\r]

\S A non-whitespace character: [^\s]

\w A word character: [a-zA-Z_0-9]

\W A non-word character: [^\w]

Quantifiers

Meaning  Greedy  Reluctant  Possessive  

X?  X??  X?+  X, once or not at all  

X*  X*?  X*+  X, zero or more times  

X+  X+?  X++  X, one or more times  

X{n}  X{n}?  X{n}+  X, exactly n times  

X{n,}  X{n,}?  X{n,}+  X, at least n times  

X{n,m}  X{n,m}?  X{n,m}+  X, at least n but not more than m times

Boundary Matchers

 ^  The beginning of a line  

$  The end of a line  

\b  A word boundary  

\B  A non-word boundary  

\A  The beginning of the input  

\G  The end of the previous match  

\Z  The end of the input but for the final terminator, if any  

\z  The end of the input

Constant Equivalent Embedded Flag Expression

Pattern.CANON_EQ  None  

Pattern.CASE_INSENSITIVE  (?i)  

Pattern.COMMENTS  (?x)  

Pattern.MULTILINE  (?m)  

Pattern.DOTALL  (?s)  

Pattern.LITERAL  None  

Pattern.UNICODE_CASE  (?u)  

Pattern.UNIX_LINES  (?d)

Oracle Database 10g Express Edition - Multiple Connections

Have you ever noticed the (apparent) limitation of Oracle Database 10g Express Edition to 10 connections (its a free product). It can be overcome.

This is how it can be done:

Open ‘Run SQL Command Line’
Digit: connect sys as sysdba (fill the password)

execute these commands:
alter system set processes = 200 scope = spfile;
alter system set sessions = 300 scope = spfile;
alter system set transactions = 350 scope = spfile;

restart the database:
shutdown immediate;
startup;
And voilá!

Change JTable column header text

Ever tried to change a column header text and the text doesn't change?

This is how it can be done:

JTable table;

DefaultTableModel model = new DefaultTableModel();

model.addColumn("Directory");

model.addColumn("Files");    

table = new JTable(model);

JScrollPane scrollPane = new JScrollPane(table);

//Changes Collumn header text

table.getColumnModel().getColumn(0).setHeaderValue("After");

table.getColumnModel().getColumn(1).setHeaderValue("Before");

                           

// Forces the header to resize and repaint itself

table.getTableHeader().resizeAndRepaint();