Find Duplicate Records MySQL Query

Hi All

I know that this is not related Liferay but i came across this useful thing during my development where you can find duplicate record from table and can delete if you need.

SELECT tablename.name FROM tablename
INNER JOIN (SELECT name FROM tablename
GROUP BY name HAVING count(name) > 1) dup_record ON tablename.name = dup_record.name

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Read Files From Folder

Hi All,

You can use below code to read files from specific folders :

import java.io.File;

public class Test {

    /**

     * @param args

     */  

public static void listFilesForFolder(File folder) {

        

        for (File fileEntry : folder.listFiles()) {

            if (fileEntry.isDirectory()) {

                listFilesForFolder(fileEntry);

            } else {

                

                System.out.println(fileEntry.getName());

            }

        }

        System.out.println("Total :" +folder.listFiles().length);

    }

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Malicious code vulnerability - Java Programming

Malicious code vulnerability - Field is a mutable array

Malicious code vulnerability - Field is a mutable Hashtable

Malicious code vulnerability - Field isn't final and can't be protected from malicious code

Malicious code vulnerability - Field isn't final but should be

Malicious code vulnerability - Field should be both final and package protected

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Performance - Java Programming

Performance - Could be refactored into a named static inner class

Performance - Could be refactored into a static inner class

Performance - Explicit garbage collection; extremely dubious except in benchmarking code

Performance - Huge string constants is duplicated across multiple class files

Performance - Inefficient use of keySet iterator instead of entrySet iterator

Performance - Maps and sets of URLs can be performance hogs

Performance - Method allocates a boxed primitive just to call toString

Performance - Method allocates an object, only to get the class object

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Avoid - Java Programming

Avoid Array Loops

Avoid Assert As Identifier

Avoid Calling Finalize

Avoid Catching NPE

Avoid Catching Throwable

Avoid Decimal Literals In Big Decimal Constructor

Avoid Duplicate Literals

Avoid Enum As Identifier

Avoid Instanceof Checks In Catch Clause

Avoid Print Stack Trace

Avoid Rethrowing Exception

Avoid Throwing Null Pointer Exception

Avoid Throwing Raw Exception Types

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Bad practice - Java Programming

Bad practice - Abstract class defines covariant compareTo() method

Bad practice - Abstract class defines covariant equals() method

Bad practice - Certain swing methods needs to be invoked in Swing thread

Bad practice - Check for sign of bitwise operation

Bad practice - Class defines clone() but doesn't implement Cloneable

Bad practice - Class defines compareTo(...) and uses Object.equals()

Bad practice - Class defines equals() and uses Object.hashCode()

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OOP Principles For The Java Designer

Here are some useful information which should be familiar with all the java programmers/designers :

1. DRY

DRY stands for Don’t Repeat Yourself, which is pretty self explanatory. This means that you shouldn’t be duplicating your code in a program. If a code fragment is appearing in two places, then you would do well to turn it into a method instead of writing the entire fragment again. Lack of duplication helps in easy maintenance of the code.

2. Encapsulation

Whether your project gets bought over or whether you work on it yourself, your code will always change. So, it is good to encapsulate the part of the code that you think will be changed. This makes you code easy to maintain and test.

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Portlet Configuration Menu Customization

If you want to modify menus which comes under portlet configuration wrench icon  then you may see below details.
Actually for each icons, its using cutome tags which is given below so you can add/modify this items here as per your requirement.

<liferay-ui:icon-menu

 align="auto"

 cssClass="portlet-options"

 direction="down"

 extended="<%= false %>"

 icon=""

 message="options"

 showArrow="<%= false %>"

 showWhenSingleIcon="<%= true %>"

>

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JVM Structure & YourKit Tool

As a java programmer, we should have at least basic knowledge of JVM and how it stores values.

The JVM memory consists of the following segments,

• Heap Memory :  Storage for Java objects
• Non-Heap Memory : Used by Java to store loaded classes and other meta-data
• Other :  JVM internal structures, loaded profiler agent code and data, etc.

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Why AngularJS

Here we have some useful information regarding AngularJS :

1) MVC Implemetation
2) User Friendly Interface

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Using Portlet Session in Liferay

Here is the sample example using login form that explains how to use PortletSession in liferay. In general PortletSession has default scope limited to Portlet which can be extended to APPLICATION_SCOPE by changing property.

Let us understand it using Login example.

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