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Saturday, 8 November 2014

APACHE TOMCAT VERTIONS NOT SHOWING IN ECLIPSE SERVER RUNTIME ENVIRONMENTS (KEPLER/LUNA INSTRUCTIONS)

Following are the steps to install Apache Tomcat and add it into Eclipse Kepler or Luna:


  1. In Eclipse Kepler, go to Help, select ‘Install New Software
  2. Choose “Kepler- http://download.eclipse.org/releases/kepler” site or add it in if it’s missing. If you’re using Luna, choose “Luna – http://download.eclipse.org/releases/luna” site or add it in if it’s missing
  3. Expand “Web, XML, and Java EE Development” section
  4. Check JST Server Adapters and JST Server Adapters Extensions
  5. Once installed, in Eclipse, go to Window / Preferences / Server / Runtime Environments
  6. Press Add button, select Apache / Apache Tomcat v7.0 or Apache Tomcat v8.∞
  7. Press Next, select location on the drive (i.e. c:\apachetomcat) for Tomcat installation directory. Make sure that the directory exist.
  8. Then press ‘Download and Install’ button, accept terms and point to your installation directory (i.e. c:\apachetomcat) and press OK button
  9. Apache TomCat v7.0 will install (you’ll see a progress in the status bar
  10. Press Finish.
  11. Apache Tomcat v7.0 or Tomcat v8.0 (depending on your selection)  will show in the list under Server Runtime Environments now.
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Saturday, 1 November 2014

How to Install Oracle Java 8 In Ubuntu

Step 1: Install Java 8 (JDK 8)


Add the webupd8team java PPA repository in our system and install Oracle java8 using following set of commands.

$ sudo add-apt-repository ppa:webupd8team/java
$ sudo apt-get update
$ sudo apt-get install oracle-java8-installer


Step 2: Verify JAVA Version


After successfully installing oracle java using above step verify installed version using following command.

$ java -version

java version "1.8.0_25"
Java(TM) SE Runtime Environment (build 1.8.0_25-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.25-b02, mixed mode)

Step 3: Setup JAVA Environment


Webupd8team is providing a package to set environment variables, Install this package using following command.

$ sudo apt-get install oracle-java8-set-default
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How To Install Java on Ubuntu

Installing default JRE/JDK

This is the recommended and easiest option. This will install OpenJDK 6 on Ubuntu 12.04 and earlier and on 12.10+ it will install OpenJDK 7.

Installing Java with apt-get is easy. First, update the package index:
sudo apt-get update

Then, check if Java is not already installed:
java -version

If it returns "The program java can be found in the following packages", Java hasn't been installed yet, so execute the following command:
sudo apt-get install default-jre

This will install the Java Runtime Environment (JRE). If you instead need the Java Development Kit (JDK), which is usually needed to compile Java applications (for example Apache Ant, Apache Maven, Eclipse and IntelliJ IDEA execute the following command:
sudo apt-get install default-jdk

That is everything that is needed to install Java.
All other steps are optional and must only be executed when needed.

Installing OpenJDK 7 (optional)

To install OpenJDK 7, execute the following command:
sudo apt-get install openjdk-7-jre

This will install the Java Runtime Environment (JRE). If you instead need the Java Development Kit (JDK), execute the following command:
sudo apt-get install openjdk-7-jdk

Installing Oracle JDK (optional)
The Oracle JDK is the official JDK; however, it is no longer provided by Oracle as a default installation for Ubuntu.

You can still install it using apt-get. To install any version, first execute the following commands:
sudo apt-get install python-software-properties
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update

Then, depending on the version you want to install, execute one of the following commands:

Oracle JDK 6
This is an old version but still in use.
sudo apt-get install oracle-java6-installer

Oracle JDK 7
This is the latest stable version.
sudo apt-get install oracle-java7-installer

Oracle JDK 8
This is a developer preview, the general release is scheduled for March 2014. This external article about Java 8 may help you to understand what it's all about.
sudo apt-get install oracle-java8-installer

Managing Java (optional)

When there are multiple Java installations on your Droplet, the Java version to use as default can be chosen. To do this, execute the following command:
sudo update-alternatives --config java

It will usually return something like this if you have 2 installations (if you have more, it will of course return more):

There are 2 choices for the alternative java (providing /usr/bin/java).

Selection    Path                                            Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-7-oracle/jre/bin/java          1062      auto mode
  1            /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java   1061      manual mode
  2            /usr/lib/jvm/java-7-oracle/jre/bin/java          1062      manual mode

Press enter to keep the current choice[*], or type selection number:
You can now choose the number to use as default. This can also be done for the Java compiler (javac):
sudo update-alternatives --config javac

It is the same selection screen as the previous command and should be used in the same way. This command can be executed for all other commands which have different installations. In Java, this includes but is not limited to: keytool, javadoc and jarsigner.

Setting the "JAVA_HOME" environment variable
To set the JAVA_HOME environment variable, which is needed for some programs, first find out the path of your Java installation:
sudo update-alternatives --config java

It returns something like:

There are 2 choices for the alternative java (providing /usr/bin/java).

Selection    Path                                            Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-7-oracle/jre/bin/java          1062      auto mode
  1            /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java   1061      manual mode
  2            /usr/lib/jvm/java-7-oracle/jre/bin/java          1062      manual mode

Press enter to keep the current choice[*], or type selection number:
The path of the installation is for each:

/usr/lib/jvm/java-7-oracle

/usr/lib/jvm/java-6-openjdk-amd64

/usr/lib/jvm/java-7-oracle

Copy the path from your preferred installation and then edit the file /etc/environment:

sudo nano /etc/environment
In this file, add the following line (replacing YOUR_PATH by the just copied path):

JAVA_HOME="YOUR_PATH"
That should be enough to set the environment variable. Now reload this file:

source /etc/environment
Test it by executing:

echo $JAVA_HOME
If it returns the just set path, the environment variable has been set successfully. If it doesn't, please make sure you followed all steps correctly.
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Tuesday, 9 September 2014

Switching between installed Java versions in ubuntu


Switching between installed Java versions can be accomplished using the update alternatives command.

  •     To get a list of your installed Java platforms, run the following command from the terminal:

    sudo update-alternatives --config java
 
  This will give you a list output similar to this:
    There are 2 choices for the alternative java (providing /usr/bin/java).
       Selection    Path                                           Priority   Status
      ------------------------------------------------------------
      0            /usr/lib/jvm/java-6-oracle/jre/bin/java         1070      auto mode
      1            /usr/lib/jvm/java-7-openjdk-i386/jre/bin/java   1051      manual mode
    * 2            /usr/lib/jvm/java-6-openjdk-i386/jre/bin/java   1069      manual mode
    Press enter to keep the current choice[*], or type selection number:

In this case, the Open JDK 6 version is running. To switch to the Open JDK version 7, you would select option 1 at the prompt and press the Enter key.

You will now be running the OpenJDK 7 version. No other changes will be needed to switch your Java versions.
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Saturday, 30 August 2014

Temporarily disable Eclipse plugins in load-on-startup

Temporarily disable Eclipse plugins in load-on-startup

Eclipse :Windows-->Preferences-->General-->Startup and Shutdown

De-select unwanted plugins.
Select Apply-->Ok.

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Thursday, 3 July 2014

Running GWT's Super Dev Mode

Super dev mode is one of the feature given in GWT after 2.5 version.

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Thursday, 19 June 2014

How do upgrade GWT in Eclipse

How do upgrade GWT in Eclipse

  • Download the GWT SDK(s) you need from https://developers.google.com/web-toolkit/versions
  • Extract it anywhere you like
  • In Eclipse Preferences > Google > Web Toolkit, use the "Add..." button and navigate to the GWT SDK directory
  • Then, in each Eclipse project's properties page (Project > Properties > Google > Web Toolkit), you can choose one of your installed SDKs.  
source
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Saturday, 14 June 2014

Eclipse (ADT) crash Failed to write core dump. Core dumps have been disabled

I found my problem here: how to fix “Failed to write core dump. Core dumps have been disabled” error while running java and here: Eclipse crashing on startup and here: Eclipse continue crash
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Tuesday, 20 May 2014

replace() vs replaceAll()

Both replace() and replaceAll() replaces all the occurrence found. However, there is difference in the type of arguments they accept.

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Thursday, 15 May 2014

What is the size of ” null ” Operator in Java ?

When you write

String st1 = null;
You create a reference “str1″ to an object that still does not exist in the heap, but when you type :

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