NetBeans Tips

Use Eclipse Shortcuts
Tools -> Options -> Keymap -> select Eclipse profile
Create code template
Tools -> Options -> Editor -> "Code Templates"
Press tab to activate define code template.
Reset the layout of windows
Windows -> Reset windows
Float/Dock views
Export/Import Settings
Open Options Dialog: Tools > Options
Click Export/Import button

In NetBeans, we can run a project, run a file, or run a test file.
Select project -> Properties -> Choose Run node -> Type command line arguments in the Arguments text box.
Remote debug
Settings in Netbeans:
Debug -> Attach Debugger
In the "Attach" dialog:
Debugger:  JPDA
Connector: Socket Attach
Transport: dt_socket
Enter host and port
Settings in server:
set JAVA_OPTS=%JAVA_OPTS% -Xrunjdwp:transport=dt_socket,address=9999,server=y,suspend=n
Update Sites

Additional Development Plugins
Latest Development Build
Static Development UC
Dynamic Development UC
Netbeans logs
Windows XP: C:\Documents and Settings\joe\.netbeans\6.7\var\log\message.log
Linux: /home/joe/.netbeans/6.7/var/log/messages.log
Mac OS X: /Users/joe/.netbeans/6.7/var/log/messages.log

JBoss Tips

Commands -S -b -c default
run.bat –Djboss.server.log.dir=d:/log
Change ports
In jboss 5, in $JBoss\server\default\conf\bindingservice.beans\META-INF\bindings-jboss-beans.xml, change the port offset of PortsDefaultBindings.
<bean name="PortsDefaultBindings"  class="">
     <!-- The port offset -->
     <!-- Set of bindings to which the "offset by X" approach can't be applied -->
To use the port assignments defined by the Ports01Bindings bean, set the jboss.service.binding.set system property to ports-01 when starting the application server.
run -c myconfig2 -Djboss.service.binding.set=ports-01
Configuring logging

The log4j configuration file is located at server/xxx/conf/jboss-log4j.xml.
Defining a rolling log appender
<appender name="FILE">
    <param name="Append" value="true"/>
    <param name="MaxFileSize" value="10MB"/>
    <param name="MaxBackupIndex" value="20"/>
    <param name="Threshold" value="ERROR"/>
Defining logging for your application
You can log your application by adding category entries to the jboss-log4j.xml file.
<appender name="JBIA" ...>
    <param name="File" value="${jboss.server.log.dir}/jbia.log"/>
<category name="org.jbia">
    <priority value="DEBUG"/>
    <appender-ref ref="JBIA" />

Edit the server.xml file. For the default server in the default location, it is ${jboss.home}\server\default\deploy\jbossweb.sar\server.xml.
Uncomment the "Access logger" section. The log file will show up in server/default/log/localhost_access_log.{todays_date}.log

<Valve className="org.apache.catalina.valves.AccessLogValve"
                prefix="localhost_access_log." suffix=".log"
                pattern="common" directory="${jboss.server.log.dir}" 
                resolveHosts="false" />

Configuring startup parameters
Rename run.bat for example to run-old.bat.
Create another run.bat file and put this line to it:
set JAVA_OPTS=%JAVA_OPTS% -Xms512m -Xmx1024m -XX:MaxPermSize=512m
run-old.bat -b -c default
Dump SOAP Messages
For the case that is not easy to model as a simple DFS request, it is useful to enable the SOAP dump.
For client side, set "";
For server side, set "";
In Jboass, put the following line in newly created run.bat:
Enable remote debug
In newly created run.bat:
rem set JAVA_OPTS=%JAVA_OPTS% -Xrunjdwp:transport=dt_socket,address=9999,server=y,suspend=n
Configure apache httpd.conf:

LoadModule proxy_module modules/
LoadModule proxy_balancer_module modules/
LoadModule proxy_ajp_module modules/
<Proxy balancer://mycluster>
Order deny,allow
Allow from all
BalancerMember http://node1.mycluster.lan:8080/ route=node1 timeout=15
BalancerMember http://node2.mycluster.lan:8080/ route=node2 timeout=15
ProxySet stickysession=JSESSIONID|jsessionid
# other values: bybusyness|byrequests|bytraffic
ProxySet lbmethod=bytraffic 
ProxyPass /jmx-console balancer://mycluster/jmx-console 
ProxyPassReverse /jmx-console  http://localhost:9080/jmx-console stickysession=JSESSIONID|jsessionid

Configure JBoss
In jboss, modify {jboss.home}\server\default\deploy\jbossweb.sar\server.xml to configure the jvmRoute for sticky sessions:
<Engine name="jboss.web" defaultHost="localhost" jvmRoute="node1">

Modify {jboss.home}\server\default\deployers\jbossweb.deployer\META-INF\war-deployers-jboss-beans.xml:
<bean name="WebAppClusteringDefaultsDeploye" class="org.jboss.web.tomcat.service.deployers.ClusteringDefaultsDeployer">
  <property name="useJK">true</property>


Useful Notepad++ Tips

Three years ago, after used Notepad++ after some time, I write one article  about NotePad++. Three years later, it's time to give it some update.
Common Settings
Open "Settings" -> "Preferences...".
In "Tab bar" section of General tab, select "Double click to close document" and "Multi-line".
In "Backup/Auto-Completion" tab, enable auto-completion option, and choose "Word completion".
Enable spell-checker
Install Aspell, afterwards enable spell-checker :)
Use "Ctrl+Tab"
Use "Ctrl+Tab" to switch between to you last viewed file, and quickly jump to the file you want.

Useful Plugins:

How to install plugins:
Go to "Plugins" -> "Plugin Manager" -> "Show Plugin Manager", this will bring up the "Plugin Manager" dialog where you can find many available plugins.
File switcher
Usually I opened many files in Notepad++, 20 - 30+, some files I need edit often, or some files I just forget to close. So sometimes, it would be hard to find files I want to edit in Notepad++.
File switcher is just the plugin that we need- It presents a sortable list, and we can type text to filter and find the file we want.

Compare Plugin - show the difference between 2 files.
XML Tools - XML Checker. Can auto-close tags and provides other useful features.
To Format XML:
Go to "Plugins" -> "XML Tools" -> "Pretty print (XML only -with line breaks) - Ctrl+Alt+Shift+B"
Explorer Plugin – a file browser
Speech Plugin
There are many other useful plugins that may meet your needs, please explore them.


Link With Editor in Eclipse

I remembered that in the old versions of eclipse(maybe 3.1), in the package and project explorer, it will show the current java class that is opened in the editor. When I change to another java class, it the explorer will automatically scroll to display the new class.

It seems this feature is gone in later release.
But the fact is that it is hidden - by default disabled, to enable it, you just need toggle the"Link with Editor" button in Package/Project/ or Navigator toolbar.


Use Working Set to group projects in Eclipse

Use Working Set to organize and group related projects visually in Eclipse

Usually, we develop or maintain different projects at same time, each project
has multiple modules, or related projects, such as test or demo projects.

We want to organize related projects visually, so in eclipse, it would look like:

To achieve this in Eclipse:
Create one working set, add related projects into it, and then (important step here), in project(or package) explorer, click the top down button -> "Top level elements" -> choose "Working Sets".


Fail to start JBoss5 - Common unexpected

Unable to start JBoss 5 - \Common was unexpected at this time

--Don't use quotes in path variable

Today, I download JBoss 5 in my Windows 7 - 64 bit machine, and try to use run.bat to start the server, but it fails, and reports error:
\Common was unexpected at this time.

Google searched, but found nothing useful.
So I tried to take a look at the run.bat, first I comment the first row "@echo off", so I will now where it stops with the error above. I located the source of the errors:
if not "x%JBOSS_NATIVE_HOME%" == "x" (
  set JAVA_OPTS=%JAVA_OPTS% "-Djava.library.path=%JBOSS_NATIVE_HOME%;%PATH%;%JBOSS_HOME%\bin"

Then I check the PATH environment:
%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;%SYSTEMROOT%\System32\WindowsPowerShell\v1.0\;"C:\Program Files (x86)\Common Files\EMC";C:\Program Files\Perforce;%JAVA_HOME%\bin;%ANT_HOME%\bin;%MVN_HOME%\bin

Yeah, find out the culprit: the quotes around the path to EMC common files - "C:\Program Files (x86)\Common Files\EMC"
After removed the quotes, start a new command line, JBoss can be started with no problem.

Lesson learned: don't put quotes in your environment variables, such as PATH, JAVA_HOME etc, this may make scripts broken. This also applies when installation program update these variables.

Java equals and hashcode

Java equals and hashcode

Obey the general contract when overriding equals
When we don't need to implement equals?
• Each instance of the class is inherently unique. This is true for classes such as Thread that represent active entities rather than values.
• You don’t care whether the class provides a “logical equality” test, java.util.Random doesn't implement equals.
• A superclass has already overridden equals, and the superclass behavior
is appropriate for this class.
• The class is private or package-private, and you are certain that its equals method will never be invoked.
One kind of value class that does not require the equals method to be overridden is a class that uses instance control(Singleton) to ensure that at most one object exists with each value. Enum types fall into this category. For these classes, logical equality is the same as object identity, so Object’s equals method functions as a logical equals method.
When is it appropriate to override Object.equals?
When a class has a notion of logical equality that differs from mere object identity and a superclass has not already overridden equals to implement the desired behavior.
Not only is overriding the equals method necessary to satisfy programmer expectations; it enables instances to serve as map keys or set elements with predictable, desirable behavior.
The equals method implements an equivalence relation. It is:
Reflexive: For any non-null reference value x, x.equals(x) must return true.
If you were to violate it and then add an instance of your class to a collection, the collection’s contains method might well say that the collection didn’t contain the instance that you just added.
Symmetric: For any non-null reference values x and y, x.equals(y) must re-
turn true if and only if y.equals(x) returns true.
public final class CaseInsensitiveString {
    private final String s;
    public CaseInsensitiveString(String s) {
       if (s == null) throw new NullPointerException();
       this.s = s;
    // Broken - violates symmetry!
    @Override public boolean equals(Object o) {
       if (o instanceof CaseInsensitiveString) return s
           .equalsIgnoreCase(((CaseInsensitiveString) o).s);
       if (o instanceof String) // One-way interoperability!
       return s.equalsIgnoreCase((String) o);
       return false;
    // To eliminate the problem, merely remove the ill-conceived attempt to
    // inter-operate with String from the equals method.
    // @Override public boolean equals(Object o) {
    // return o instanceof CaseInsensitiveString
    // && ((CaseInsensitiveString) o).s.equalsIgnoreCase(s);
    // }
    public static void main(String[] args) {
       CaseInsensitiveString cis = new CaseInsensitiveString(“Polish”);
       String s = “polish”;
       List list = new ArrayList();
       // this would depend on how contains is implemented.
       // it calls CaseInsensitiveString.equals(true), or String.equals(false)
       // in sun jdk, it would return false.
Transitive: For any non-null reference values x, y, z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) must return true.
Consider the case of a subclass that adds a new value component to its superclass, the subclass adds a piece of information that affects equals comparisons.
There is no way to extend an instantiable class and add a value component while preserving the equals contract, unless you are willing to forgo the benefits of object-oriented abstraction.
public class ColorPoint extends Point {
    private final Color color;
    public ColorPoint(int x, int y, Color color) {
       super(x, y);
       this.color = color;
    // Broken - violates symmetry!
    // System.err.println(p.equals(cp)); // return true
    // System.err.println(cp.equals(p)); // return false
    // @Override public boolean equals(Object o) {
    // if (!(o instanceof ColorPoint)) return false;
    // return super.equals(o) && ((ColorPoint) o).color == color;
    // }
    // Broken - violates transitivity!
    // System.err.println(p1.equals(p2));// return true
    // System.err.println(p3.equals(p2));// return true
    // System.err.println(p1.equals(p3));// return false
    // @Override public boolean equals(Object o) {
    // if (!(o instanceof Point)) return false;
    // // If o is a normal Point, do a color-blind comparison
    // if (!(o instanceof ColorPoint)) return o.equals(this);
    // // o is a ColorPoint; do a full comparison
    // return super.equals(o) && ((ColorPoint) o).color == color;
    // }
    // Broken - violates Liskov substitution principle (page 40)
    @Override public boolean equals(Object o) {
       if (o == null || o.getClass() != getClass()) return false;
       ColorPoint p = (ColorPoint) o;
       return p.getX() == getX() && p.getY() == getY()
           && p.getColor() == getColor();
    public static void main(String[] args) {
       ColorPoint p1 = new ColorPoint(1, 2, Color.RED);
       Point p2 = new Point(1, 2);
       ColorPoint p3 = new ColorPoint(1, 2, Color.RED);
       System.err.println(p1.equals(p2));// return false
       System.err.println(p3.equals(p2));// return false
       System.err.println(p1.equals(p3));// return true
    public Color getColor() {
       return color;
Consistent: For any non-null reference values x and y, multiple invocations
of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
• For any non-null reference value x, x.equals(null) must return false, all objects must be unequal to null.
public abstract class AbstractList extends AbstractCollection implements List {
  public boolean equals(Object o) {
    if (o == this)
      return true;
    if (!(o instanceof List))
      return false;
    ListIterator e1 = listIterator();
    ListIterator e2 = ((List) o).listIterator();
    while(e1.hasNext() && e2.hasNext()) {
      E o1 =;
      Object o2 =;
      if (!(o1==null ? o2==null : o1.equals(o2)))
       return false;
    return !(e1.hasNext() || e2.hasNext());
  public int hashCode() {
    int hashCode = 1;
    Iterator i = iterator();
    while (i.hasNext()) {
      E obj =;
      hashCode = 31*hashCode + (obj==null ? 0 : obj.hashCode());
    return hashCode;
List ia = new ArrayList();
List ib = new LinkedList();
System.err.println(ia.equals(ib)); // return true
To implement high-quality equals method:
1. Use the == operator to check if the argument is a reference to this object.
If so, return true. This is just a performance optimization, but one that is worth doing if the comparison is potentially expensive.
2. Use the instanceof operator to check if the argument has the correct type.
If not, return false. Typically, the correct type is the class in which the method occurs. Occasionally, it is some interface implemented by this class.
3. Cast the argument to the correct type.
4. For each “significant” field in the class, check if that field of the argument matches the corresponding field of this object.
For primitive fields whose type is not float or double, use the == operator for comparisons; for object reference fields, invoke the equals method recursive-
ly; for float fields, use the method; and for double fields, use
5. When you are finished writing your equals method, ask yourself three questions: Is it symmetric? Is it transitive? Is it consistent? And don’t just ask yourself; write unit tests to check that these properties hold! If they don’t, figure out why not, and modify the equals method accordingly
Always override hashCode when you override equals
Don’t substitute another type for Object in the equals declaration.
You must override hashCode in every class that overrides equals. Failure to do so will result in a violation of the general contract for Object.hashCode, which will prevent your class from functioning properly in conjunction with all hash-based collections, including HashMap, HashSet, and Hashtable.
Here is the contract, copied from the Object specification [JavaSE6]:
Whenever it is invoked on the same object more than once during an execution of an application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execu-
tion of an application to another execution of the same application.
If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
It is not required that if two objects are unequal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.
Equal objects must have equal hash codes.
Objects with equal hashcode is not required to be equal.
What would happen if 2 equals object have different hashcode? CRUDJ
2 equals object would be insert into same hashmap, we can query it and delete it.
Map m = new HashMap();
m.put(new PhoneNumber(707, 867, 5309), “Jenny”);
// return null
System.err.println(m.get(new PhoneNumber(707, 867, 5309)));
// return false
System.err.println(m.containsKey(new PhoneNumber(707, 867, 5309)));
m.put(new PhoneNumber(707, 867, 5309), “Jenny”);
System.err.println(m.size()); // return 2
System.err.println(m.size()); // return 2
The get method is likely to look for the phone number in a different hash bucket from the one in which it was stored by the put method. Even if the two instances happen to hash to the same bucket, the get method will almost certainly return null, as HashMap has an optimization that caches the hash code associated with each entry and doesn’t bother checking for object equality if the hash codes don’t match.
What if 2 un-equal objects have same hashcode?
This would decrease hashset. hashmap performance.
// The worst possible legal hash function - never use!
@Override public int hashCode() { return 42; }
Hash tables degenerate to linked lists.
A good hash function tends to produce unequal hash codes for unequal objects.
Ideally, a hash function should distribute any reasonable collection of unequal instances uniformly across all possible hash values.
Do not be tempted to exclude significant parts of an object from the hash code computation to improve performance.
Principals to implement hashcode:
1. Store some constant nonzero value, say, 17, in an int variable called result.
2. For each significant field f in your object (each field taken into account by the equals method, that is), do the following:
a. Compute an int hash code c for the field:
i. If the field is a boolean, compute (f?1:0).
ii. If the field is a byte, char, short, or int, compute (int) f.
iii. If the field is a long, compute (int) (f ^ (f >>> 32)).
iv. If the field is a float, compute Float.floatToIntBits(f).
v. If the field is a double, compute Double.doubleToLongBits(f), and then hash the resulting long as in step 2.a.iii.
vii. If the field is an array, treat it as if each element were a separate field.
That is, compute a hash code for each significant element by applying
these rules recursively, and combine these values per step 2.b. If every
element in an array field is significant, you can use one of the
Arrays.hashCode methods added in release 1.5.
b. Combine the hash code c computed in step 2.a into result as follows:
    result = 31 * result + c;
3. Return result.
4. When you are finished writing the hashCode method, ask yourself whether equal instances have equal hash codes. Write unit tests to verify your intuition!
If equal instances have unequal hash codes, figure out why and fix the problem.
You must exclude any fields that are not used in equals comparisons, or you risk violating the second provision of the hashCode contract.

The multiplication in step 2.b makes the result depend on the order of the fields, yielding a much better hash function if the class has multiple similar fields.

The multiplication in step 2.b makes the result depend on the order of the fields, yielding a much better hash function if the class has multiple similar fields.
For example, if the multiplication were omitted from a String hash function, all anagrams would have identical hash codes. The value 31 was chosen because it is an odd prime. If it were even and the multiplication overflowed, information would be lost, as multiplication by 2 is equivalent to shifting. The advantage of using a prime is less clear, but it is traditional. A nice property of 31 is that the multiplication can be replaced by a shift and a subtraction for better performance:
31*i==(i<<5)-i. Modern VMs do this sort of optimization automatically.


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