Let’s look at some of the most recurring errors by freshmen.

Illegal Type Assignment

Java restricts its users to assign only the same type of variables. On a simpler note, you can not assign an “Integer” type value to a “Double” type variable.

Example

Output

Solution

Replace line 5 of the above program for casting in to double. Test the output in your IDE.

Invalid Return Type

By the rules of the Java language, you can only return the type of variable specified as the return type. A void type method is not capable of returning a String if you try to do so. And hence, you will get a compile-time error.

Example

Output

Solution

Invalid Arguments Type

Let’s say you define a method passing two arguments. This method takes two integers to find their sum. Now if you try to pass two floating points in place of two integers, java will give you a compile-time error.

Example

Output

Solution

Null Pointer Exceptions

These are most redundant and tricky to handle as a novice. However, there’s no rocket science behind it if you take care of some fundamentals. A null pointer exception arises when you try to access a resource whose value is null and not initialized to a concrete value. Majorly, the null pointer is used to allocate a unique reference to a resource. If you do not have such a requirement then make sure all values are initialized properly before accessing them.

Example 1

Output 1

Solution 1

Example 2

Output 2

Solution 2

Another advanced way to resolve un-checked exceptions like null pointer exceptions is the exception handling mechanism in Java. Feel free to check out java exceptions examples for a more profound understanding.

Syntax Errors

Anything that does not comply with the Java language rules is categorized as a syntax error.
From beginners to experts, we all are guilty of it at some point. If you have just started working in Java, you must comprehend what I’m talking about. The analogy of syntax rules can be grammatical rules in the English language. The syntax is defined to maintain the standards across the board. Not following naming conventions, misplaced semicolons, un-balanced parenthesis, and misspelled method names, etc are some of the typical syntax errors.

Example

Output

Solution

Conclusion

By this point, you must be aware of the most recurring java errors of beginners. It’s okay to have loads of errors when you start learning. The key is not to get afraid of them, and rather keep improving yourself. Till then, keep growing! 🙂

The post Top 5 Java Errors with Solutions appeared first on Linux Windows and android Tutorials.

Java is one of the preferred languages by many developers but it is also necessary to run other very important software. In this sense, Oracle from time to time releases a new version that includes good news.

So, if you are a developer and want to try Java on Debian 11, this post will help you with that.

Install Java on Debian 11

In the Debian 11 stable repositories we have the presence of OpenJDK which is a free Java implementation. We will be able to use and install it without compatibility problems because it is the same as the version distributed by Oracle.

For the sake of stability and compatibility with most applications, Debian 11 includes Java 11. This version besides being LTS is the base on which many important applications have been built.

So, this is the version we will install.

To install both the JDK (Java Development Kit) and the JRE (Java Runtime Environment) just execute in a terminal this pair of commands

sudo apt update
sudo apt install default-jdk
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
  ca-certificates-java default-jdk-headless default-jre default-jre-headless fontconfig-config fonts-dejavu-core java-common libasound2 libasound2-data
  libavahi-client3 libavahi-common-data libavahi-common3 libcups2 libdrm-amdgpu1 libdrm-common libdrm-intel1 libdrm-nouveau2 libdrm-radeon1 libdrm2 libfontconfig1
  libgif7 libgl1 libgl1-mesa-dri libglapi-mesa libglvnd0 libglx-mesa0 libglx0 libgraphite2-3 libharfbuzz0b libjpeg62-turbo liblcms2-2 libllvm11 libnspr4 libnss3
  libpciaccess0 libpcsclite1 libsensors-config libsensors5 libvulkan1 libx11-6 libx11-data libx11-xcb1 libxau6 libxcb-dri2-0 libxcb-dri3-0 libxcb-glx0 libxcb-present0
  libxcb-shm0 libxcb-sync1 libxcb-xfixes0 libxcb1 libxdamage1 libxdmcp6 libxext6 libxfixes3 libxi6 libxrender1 libxshmfence1 libxtst6 libxxf86vm1 libz3-4
  openjdk-11-jdk openjdk-11-jdk-headless openjdk-11-jre openjdk-11-jre-headless x11-common
Suggested packages:
  libasound2-plugins alsa-utils cups-common liblcms2-utils pciutils pcscd lm-sensors openjdk-11-demo openjdk-11-source visualvm libnss-mdns fonts-dejavu-extra
  fonts-ipafont-gothic fonts-ipafont-mincho fonts-wqy-microhei | fonts-wqy-zenhei fonts-indic
Recommended packages:
  alsa-ucm-conf alsa-topology-conf mesa-vulkan-drivers | vulkan-icd libxt-dev libatk-wrapper-java-jni fonts-dejavu-extra
The following NEW packages will be installed:
  ca-certificates-java default-jdk default-jdk-headless default-jre default-jre-headless fontconfig-config fonts-dejavu-core java-common libasound2 libasound2-data
  libavahi-client3 libavahi-common-data libavahi-common3 libcups2 libdrm-amdgpu1 libdrm-common libdrm-intel1 libdrm-nouveau2 libdrm-radeon1 libdrm2 libfontconfig1
  libgif7 libgl1 libgl1-mesa-dri libglapi-mesa libglvnd0 libglx-mesa0 libglx0 libgraphite2-3 libharfbuzz0b libjpeg62-turbo liblcms2-2 libllvm11 libnspr4 libnss3
  libpciaccess0 libpcsclite1 libsensors-config libsensors5 libvulkan1 libx11-6 libx11-data libx11-xcb1 libxau6 libxcb-dri2-0 libxcb-dri3-0 libxcb-glx0 libxcb-present0
  libxcb-shm0 libxcb-sync1 libxcb-xfixes0 libxcb1 libxdamage1 libxdmcp6 libxext6 libxfixes3 libxi6 libxrender1 libxshmfence1 libxtst6 libxxf86vm1 libz3-4
  openjdk-11-jdk openjdk-11-jdk-headless openjdk-11-jre openjdk-11-jre-headless x11-common
0 upgraded, 67 newly installed, 0 to remove and 2 not upgraded.
Need to get 306 MB of archives.
After this operation, 574 MB of additional disk space will be used.
Do you want to continue? [Y/n]

In case you only want to install the JRE which is enough to run certain applications made with Java,

sudo apt install default-jre

At the end of the process, Java will be installed on your computer.

Configuring the Environment Variable

Once Java is installed, it is a good idea to set the JAVA_HOME environment variable that tells the system the path where Java is installed. This step, although optional for this post, may be necessary when installing more complex applications.

So, to know where JAVA is installed, just run the following command

sudo update-alternatives --config java

There you will be shown a screen where you can choose between several versions of Java installed. Of course, in this case, you should only see version 11 that was installed, but the important thing is that it will also show you the path where it will be.

In this case OpenJDK 11 is located at /usr/lib/jvm/java-11-openjdk-amd64/bin/java.

With this information, we can edit the /etc/environment file.

sudo nano /etc/environment

And add the following to the end of the file

JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64"

Save the changes and close the text editor.

Apply the changes

source /etc/environment

Finally, the environment variable has been set correctly. To demonstrate this, run

echo $JAVA_HOME

Sample Output:

/usr/lib/jvm/java-11-openjdk-amd64

So, Java is installed without problems. Enjoy it!

The post Install Java on Debian 11 appeared first on Linux Windows and android Tutorials.

According to the Wildfly website:

WildFly is a flexible, lightweight, managed application runtime that helps you build amazing applications.

Being Java-based, it is compatible with many operating systems such as Linux, macOS, and Windows. In addition to this, it is open source which can help us with licensing issues.

So, now you will learn how to install it on a Debian 10 server or your computer for development.

Install Wildfly on Debian 10

Before we start, open a terminal and update Debian 10. In this post, we will use sudo if you don’t know how to enable it in Debian, we tell you in this post.

sudo apt update
sudo apt upgrade

Now it is time to install Java if you don’t have it on your system.

sudo apt install default-jdk
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
  ca-certificates-java default-jdk-headless default-jre default-jre-headless fontconfig-config fonts-dejavu-core java-common libasound2 libasound2-data
  libavahi-client3 libavahi-common-data libavahi-common3 libcups2 libdrm-amdgpu1 libdrm-common libdrm-intel1 libdrm-nouveau2 libdrm-radeon1 libdrm2 libfontconfig1
  libgif7 libgl1 libgl1-mesa-dri libglapi-mesa libglvnd0 libglx-mesa0 libglx0 libgraphite2-3 libharfbuzz0b libjpeg62-turbo liblcms2-2 libllvm7 libnspr4 libnss3
  libpciaccess0 libpcsclite1 libsensors-config libsensors5 libx11-6 libx11-data libx11-xcb1 libxau6 libxcb-dri2-0 libxcb-dri3-0 libxcb-glx0 libxcb-present0
  libxcb-sync1 libxcb1 libxdamage1 libxdmcp6 libxext6 libxfixes3 libxi6 libxrender1 libxshmfence1 libxtst6 libxxf86vm1 openjdk-11-jdk openjdk-11-jdk-headless
  openjdk-11-jre openjdk-11-jre-headless x11-common
Suggested packages:
  libasound2-plugins alsa-utils cups-common liblcms2-utils pciutils pcscd lm-sensors openjdk-11-demo openjdk-11-source visualvm libnss-mdns fonts-dejavu-extra
  fonts-ipafont-gothic fonts-ipafont-mincho fonts-wqy-microhei | fonts-wqy-zenhei fonts-indic
Recommended packages:
  libxt-dev libatk-wrapper-java-jni fonts-dejavu-extra
The following NEW packages will be installed:
  ca-certificates-java default-jdk default-jdk-headless default-jre default-jre-headless fontconfig-config fonts-dejavu-core java-common libasound2 libasound2-data
  libavahi-client3 libavahi-common-data libavahi-common3 libcups2 libdrm-amdgpu1 libdrm-common libdrm-intel1 libdrm-nouveau2 libdrm-radeon1 libdrm2 libfontconfig1
  libgif7 libgl1 libgl1-mesa-dri libglapi-mesa libglvnd0 libglx-mesa0 libglx0 libgraphite2-3 libharfbuzz0b libjpeg62-turbo liblcms2-2 libllvm7 libnspr4 libnss3
  libpciaccess0 libpcsclite1 libsensors-config libsensors5 libx11-6 libx11-data libx11-xcb1 libxau6 libxcb-dri2-0 libxcb-dri3-0 libxcb-glx0 libxcb-present0
  libxcb-sync1 libxcb1 libxdamage1 libxdmcp6 libxext6 libxfixes3 libxi6 libxrender1 libxshmfence1 libxtst6 libxxf86vm1 openjdk-11-jdk openjdk-11-jdk-headless
  openjdk-11-jre openjdk-11-jre-headless x11-common
0 upgraded, 63 newly installed, 0 to remove and 26 not upgraded.
Need to get 289 MB of archives.
After this operation, 637 MB of additional disk space will be used.
Do you want to continue? [Y/n]

It is recommended to create a new user and group for Wildfly so that it does not interfere with the others. First, create a group like this

sudo groupadd -r wildfly

Now create the user:

sudo useradd -r -g wildfly -d /opt/wildfly -s /sbin/nologin wildfly

From the previous command, we can deduce that you will not be able to log in but you will have permission over the directory /opt/wildfly.

Now yes, from the /tmp folder, you can download Wildlfly

cd /tmp/
wget -c https://download.jboss.org/wildfly/24.0.0.Final/wildfly-24.0.0.Final.tar.gz
--2021-07-13 16:47:17--  https://download.jboss.org/wildfly/24.0.0.Final/wildfly-24.0.0.Final.tar.gz
Resolving download.jboss.org (download.jboss.org)... 2a02:26f0:6c00::210:bb8b, 2a02:26f0:6c00::210:bb58, 104.126.36.121, ...
Connecting to download.jboss.org (download.jboss.org)|2a02:26f0:6c00::210:bb8b|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 210418338 (201M) [application/x-gzip]
Saving to: ‘wildfly-24.0.0.Final.tar.gz’

wildfly-24.0.0.Final.tar.gz               100%[=====================================================================================>] 200.67M  40.7MB/s    in 4.8s

2021-07-13 16:47:22 (42.0 MB/s) - ‘wildfly-24.0.0.Final.tar.gz’ saved [210418338/210418338]

At the time of writing this post, the latest stable version of Wildfly is 24.0.0 so this command will change when a new version is released.

Then, decompress it

sudo tar xfv wildfly-24.0.0.Final.tar.gz -C /opt/

Make a symbolic link from the folder to another folder with an easier-to-remember name.

sudo ln -s /opt/wildfly-24.0.0.Final/ /opt/wildfly

Make the user wildfly the owner of the folder.

sudo chown -RH wildfly: /opt/wildfly

Configuring WildFly on Debian 10

By default, the package we have downloaded includes a configuration file that we have to enable. To do this, create a folder called wildfly in the /etc/ path.

sudo mkdir -p /etc/wildfly

And to enable the default Wildfly configuration, copy the example file to this directory.

sudo cp /opt/wildfly/docs/contrib/scripts/systemd/wildfly.conf /etc/wildfly/

Also, copy the startup script into the bin folder of the dedicated Wildfly folder.

sudo cp /opt/wildfly/docs/contrib/scripts/systemd/systemd/launch.sh /opt/wildfly/bin/

After this, assign run permissions to the script.

sudo sh -c 'chmod +x /opt/wildfly/bin/*.sh'

To start, restart and stop running Wildfly then it is best to do it via systemd, and then we have to create a new service for it. Fortunately, the downloaded package includes one so we have to copy it to the directory where the service configurations are hosted.

sudo cp /opt/wildfly/docs/contrib/scripts/systemd/wildfly.service /etc/systemd/system/

Now, refresh the list of services

sudo systemctl daemon-reload

And start the service

sudo systemctl start wildfly

Also, you can check the service for any errors.

sudo systemctl status wildfly
● wildfly.service - The WildFly Application Server
   Loaded: loaded (/etc/systemd/system/wildfly.service; disabled; vendor preset: enabled)
   Active: active (running) since Tue 2021-07-13 16:52:28 CEST; 2s ago
 Main PID: 4978 (launch.sh)
    Tasks: 69 (limit: 4915)
   Memory: 196.4M
   CGroup: /system.slice/wildfly.service
           ├─4978 /bin/bash /opt/wildfly/bin/launch.sh standalone standalone.xml 0.0.0.0
           ├─4979 /bin/sh /opt/wildfly/bin/standalone.sh -c standalone.xml -b 0.0.0.0
           └─5074 java -D[Standalone] -server -Xms64m -Xmx512m -XX:MetaspaceSize=96M -XX:MaxMetaspaceSize=256m -Djava.net.preferIPv4Stack=true -Djboss.modules.system.pkJul 13 16:52:28 osradar systemd[1]: Started The WildFly Application Server.

All that remains is to create the user with administrative permissions. To do this, run a script called add-user.sh.

After entering the username, and answering a few more questions, you will be assigned a password.

To represent the user add the following to the server-identities definition <secret value="YW5nZWxv" />

This way, you can open your web browser and visit http://localhost:8080 or if you installed on a server http://your-server:8080 and see this screen.

So, Wildfly is correctly installed.

Optional: Enable the administrative panel remotely

The administrative panel can be accessed from http://localhost:9990/console but if you installed Wildfly on a remote server, this will not work because, by default, this feature is disabled remotely.

So, you can enable it. To do this, edit the Wildfly configuration file

sudo nano /etc/wildfly/wildfly.conf

And add the following line at the end.

WILDFLY_CONSOLE_BIND=0.0.0.0.0

Save the changes and close the editor.

Now edit the WildFly startup script

sudo nano /opt/wildfly/bin/launch.sh

And replace the lines inside the second if that start with $WILDFLY_HOME with the following lines

$WILDFLY_HOME/bin/domain.sh -c $2 -b $3 -bmanagement $4
else
$WILDFLY_HOME/bin/standalone.sh -c $2 -b $3 -bmanagement $4

Save the changes and close the editor.

After this, you need to modify something in the file that manages the Wildfly service.

sudo nano /etc/systemd/system/wildfly.service

Change the ExecStart line to this one

ExecStart=/opt/wildfly/bin/launch.sh $WILDFLY_MODE $WILDFLY_CONFIG $WILDFLY_BIND $WILDFLY_CONSOLE_BIND $WILDFLY_CONSOLE_BIND

Refresh all daemons and restart the service.

sudo systemctl daemon-reload
sudo systemctl restart wildfly

You will now be able to remotely access your configuration panel.

Conclusion

Developing Java applications requires tools to help with the process. In this case, we have presented you with one that allows you to set up a JavaEE application server, and with Wildfly’s extensive experience we will have mature and production-ready software.

Enjoy it.

The post Install Wildfly (JBoss) on Debian 10 appeared first on Linux Windows and android Tutorials.

What is Play Framework?

Play Framework is a framework that allows us to make web applications with Java & Scala in a fast and easy way. These applications are based on scalability and the possibility that they can be adapted to many different needs.

Like many current frameworks, it uses the MVC pattern for the logical processing of the applications. In addition to this, it has a lot of community support as well as brilliant official documentation.

So with this introduction to Play, we can start the installation process.

Install Play Framework on Debian 10

Normally you would install this framework on a local computer, but it also works on a remote server.

So, open a terminal and update Debian

sudo apt update
sudo apt upgrade

After that, you can install some necessary packages. Normally you should already have them but it’s always good to be sure.

sudo apt install git unzip zip curl

Then, with the curl command we have to download the SDK install script with which we will install sbt which is the tool with which we will finally manage the projects made with Play Framework.

curl -s "https://get.sdkman.io" | bash

At the end of the process, it is necessary to refresh the user’s PATH.

source "$HOME/.sdkman/bin/sdkman-init.sh"

Now check the installed SDK version with the following command:

sdk version

Sample Output

==== BROADCAST =================================================================
* 2021-07-02: grails 3.3.14 available on SDKMAN!
* 2021-07-02: gradle 7.1.1 available on SDKMAN!
* 2021-07-01: grails 3.3.13 available on SDKMAN!
================================================================================

SDKMAN 5.11.6

When using the SDK, you should then install Java. To do this, you can run the following command:

sdk install java $(sdk list java | grep -o "8\.[0-9]*\.[0-9]*\.hs-adpt" | head -1)

Sample output:

Done repackaging...

Installing: java 8.0.292.hs-adpt
Done installing!


Setting java 8.0.292.hs-adpt as default.

now it uses SDK to install sbt.

sdk install sbt

Sample Output:

Installing: sbt 1.5.4
Done installing!

Setting sbt 1.5.4 as default.

Download the sample project for Play Framework

Make sure you are in your home folder and from there with the git command download the sample project.

cd ~
git clone https://github.com/playframework/play-samples.git
Cloning into 'play-samples'...
remote: Enumerating objects: 16564, done.
remote: Counting objects: 100% (362/362), done.
remote: Compressing objects: 100% (246/246), done.
remote: Total 16564 (delta 210), reused 199 (delta 105), pack-reused 16202
Receiving objects: 100% (16564/16564), 5.32 MiB | 12.35 MiB/s, done.
Resolving deltas: 100% (9846/9846), done.

Access the downloaded folder

cd play-samples/play-scala-hello-world-tutorial

And run the project

sbt run

This will make it available at http://localhost:9000 which you can use a web browser to view the content.

Now if you are doing this installation on a remote server, then you will get an error. This is because the host has not been authorized.

Finish running Play and edit the configuration file:

nano /home/user/play-samples/play-scala-hello-world-tutorial/conf/application.conf

And add the following:

play.filters.hosts {
  allowed = ["."]
}

Save the changes and close the editor so that when you start the framework again, it will be accessible.

Creating a new application with Play Framework on Debian 10

First, create a folder for the new project. In my case I will call it example but you can call it whatever you want. Then access it.

mkdir ~/example
cd ~/example

And from there, you can download the template for java application development:

sbt new playframework/play-java-seed.g8

Now, access the generated folder and run it:

cd example
run

Stop it and start working on it.

Conclusion

In this post, you learned about the existence of a very interesting framework for the web like Play Framework. Besides this you are now able to install it on Debian 10.

Enjoy it.

The post Install Play framework on Debian 10 appeared first on Linux Windows and android Tutorials.

First step

Download and install Oracle Java for Windows, macOS, or Linux, depending on your operating system.

Second step

Once you have installed Java, download the tool which is a .jar executable file by following the link below:

Xiaomi ADB Tools

Third step

After that, enable USB debugging on your phone by following the steps below:

• Open the settings of your phone
• Go to About phone
• Click seven times on MIUI version
• Now go to “additional settings”, where you will find the developer options
• Enable USB debugging

Fourth step

Then connect your phone to your PC and allow USB debugging permissions. After it has successfully connected, you will see a list of apps and services that can be uninstalled. Remember that you can delete apps without fear, as all selectable apps in the tool are not necessary for the proper functioning of the phone.

Fifth step

Finally, select the apps you want to uninstall and press the Uninstall! button. Also in case you want you can easily reinstall them using the Reinstaller section.

Conclusion

Xiaomi phones are excellent, yet you can always improve their performance without going to the extreme of installing a Custom Rom (practically replace the entire operating system). An alternative to optimize them is Xiaomi ADB Tools with a simple and secure interface, you can free up space and gain smoothness. Thanks for reading us. Bye!

The post How to clean all MIUI Bloatware with Xiaomi ADB Tools appeared first on Linux Windows and android Tutorials.

Java is one of the preferred languages by many developers but it is also necessary to run other very important software. In this sense, Oracle from time to time releases a new version that includes good news.

So, if you are a developer and want to try Java 16 on Debian 10, this post will help you with that.

Install Oracle Java 16 on Debian 10

There is a package created by Linux Uprising that facilitates the whole process. This package is originally created for Ubuntu but we can also use it in Debian.

In a very brief way, the package is an installer that takes care of downloading the Oracle binaries. Also, it extracts them and copies them in the appropriate directory and everything by us.

So, open a terminal or log in with SSH and update the distribution

sudo apt update
sudo apt upgrade

Then, download the package that will help us with the installation:

wget -c https://launchpad.net/~linuxuprising/+archive/ubuntu/java/+files/oracle-java16-installer_16-1~linuxuprising0_amd64.deb -O java.deb
--2021-03-17 23:36:18--  https://launchpad.net/~linuxuprising/+archive/ubuntu/java/+files/oracle-java16-installer_16-1~linuxuprising0_amd64.deb
 Resolving launchpad.net (launchpad.net)… 2001:67c:1560:8003::8004, 2001:67c:1560:8003::8003, 91.189.89.223, …
 Connecting to launchpad.net (launchpad.net)|2001:67c:1560:8003::8004|:443… connected.
 HTTP request sent, awaiting response… 303 See Other
 Location: https://launchpadlibrarian.net/528398753/oracle-java16-installer_16-1~linuxuprising0_amd64.deb [following]
 --2021-03-17 23:36:19--  https://launchpadlibrarian.net/528398753/oracle-java16-installer_16-1~linuxuprising0_amd64.deb
 Resolving launchpadlibrarian.net (launchpadlibrarian.net)… 2001:67c:1560:8003::8008, 2001:67c:1560:8003::8007, 91.189.89.229, …
 Connecting to launchpadlibrarian.net (launchpadlibrarian.net)|2001:67c:1560:8003::8008|:443… connected.
 HTTP request sent, awaiting response… 200 OK
 Length: 33962 (33K) [application/x-debian-package]
 Saving to: ‘java.deb’
 java.deb                                   100%[=====================================================================================>]  33.17K  --.-KB/s    in 0.02s   
 2021-03-17 23:36:19 (1.50 MB/s) - ‘java.deb’ saved [33962/33962]

When the download is complete, it must be run or installed:

sudo apt install ./java.deb
Reading package lists… Done
 Building dependency tree       
 Reading state information… Done
 Note, selecting 'oracle-java16-installer' instead of './java.deb'
 The following additional packages will be installed:
   binutils binutils-common binutils-x86-64-linux-gnu java-common libbinutils
 Suggested packages:
   binutils-doc binfmt-support visualvm ttf-baekmuk | ttf-unfonts | ttf-unfonts-core ttf-kochi-gothic | ttf-sazanami-gothic ttf-kochi-mincho | ttf-sazanami-mincho
   ttf-arphic-uming firefox | firefox-2 | iceweasel | mozilla-firefox | iceape-browser | mozilla-browser | epiphany-gecko | epiphany-webkit | epiphany-browser | galeon
   | midbrowser | moblin-web-browser | xulrunner | xulrunner-1.9 | konqueror | chromium-browser | midori | google-chrome
 Recommended packages:
   gsfonts-x11 oracle-java16-set-default
 The following NEW packages will be installed:
   binutils binutils-common binutils-x86-64-linux-gnu java-common libbinutils oracle-java16-installer
 0 upgraded, 6 newly installed, 0 to remove and 5 not upgraded.
 Need to get 4,446 kB/4,480 kB of archives.
 After this operation, 28.4 MB of additional disk space will be used.
 Do you want to continue? [Y/n]

And there the whole process will begin

First, accept the license terms:

And then the process will continue. In the end, you will see an output like the following

Now to make this version of Java the default you have to download another package:

wget https://launchpad.net/~linuxuprising/+archive/ubuntu/java/+files/oracle-java16-set-default_16-1~linuxuprising0_all.deb -O default.deb

And install it:

sudo apt install ./default.deb

Now yes, check the Java version of the system to see if everything went well:

java --version

Output:

java 16 2021-03-16
 Java(TM) SE Runtime Environment (build 16+36-2231)
 Java HotSpot(TM) 64-Bit Server VM (build 16+36-2231, mixed mode, sharing)

So, enjoy it.

Conclusion

Java 16 has been released with many new features and this makes many want to leap an old version to this one. Therefore, in this post, you could learn how to install it in Ubuntu.

The post How to install Oracle Java 16 on Debian 10 appeared first on Linux Windows and android Tutorials.

Apache Tomcat

Java and its multipurpose language and that make it so good and useful to learn. Well, after coding your web application, it gets to the point where you have to deploy it. To do this, it requires a server that can interpret that Java code. Remember that we are talking about web applications. And to deploy and serve it, nothing like Apache Tomcat.

Estricatemente speaking Tomcat is not a server but transforms the caught JPS into servlets that can serve the application in question.

On the other hand, Apache Tomcat is open source and can be installed on any system running Java.

Install Apache Tomcat on Ubuntu 20.04 / Debian 10

1) Install and configure Java on Ubuntu 20.04 / Debian 10

Apache Tomcat is an application made with Java. Therefore, the first step is to install Java on Debian 10.

Open a terminal session and run the following:

:~$ sudo apt install default-jre default-jdk

Then, check the java version.

:~$ java --version
openjdk 11.0.3 2019-04-16
OpenJDK Runtime Environment (build 11.0.3+7-post-Debian-5)
OpenJDK 64-Bit Server VM (build 11.0.3+7-post-Debian-5, mixed mode, sharing)

As you can see, Java version 11 has been installed. It is one of the most recent and with very good support.

Now, you have to modify the /etc/environment file and add the Java path.

:~$ sudo nano /etc/environment

And add the following:

JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64/"

Save the changes and close the file.

The next step is to edit the .bashrc file and add the following:

:~$ sudo nano .bashrc

export JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64/"
export PATH=$JAVA_HOME/bin:$PATH

Again, save the changes and close the file.

Next, refresh the bash.

:~$ source .bashrc

Now, type this command to test the Java path.

:~$ echo $JAVA_HOME
/usr/lib/jvm/java-11-openjdk-amd64/bin/java

So, if you got the Java path from your computer, everything is correct.

2) Install Apache Tomcat on Ubunut 20.04 / Debian 10

For security reasons, it is convenient to create a new user for Tomcat. Also, add it to a group called tomcat.

:~$ sudo -i
:~# groupadd tomcat
:~# useradd -s /bin/false -g tomcat -d /opt/tomcat tomcat

Now we can install Apache Tomcat. To do this, go to the /opt/ folder and download with wget.

:~# cd /opt/
:~# wget -c https://downloads.apache.org/tomcat/tomcat-9/v9.0.39/bin/apache-tomcat-9.0.39.tar.gz
--2020-10-28 19:23:24-- https://downloads.apache.org/tomcat/tomcat-9/v9.0.39/bin/apache-tomcat-9.0.39.tar.gz
Resolving downloads.apache.org (downloads.apache.org)... 88.99.95.219, 2a01:4f8:10a:201a::2
Connecting to downloads.apache.org (downloads.apache.org)|88.99.95.219|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 11282879 (11M) [application/x-gzip]
Saving to: ‘apache-tomcat-9.0.39.tar.gz’
apache-tomcat-9.0.39.tar.gz 100%[=====================================================================================>] 10.76M 157KB/s in 1m 49s
2020-10-28 19:25:15 (101 KB/s) - ‘apache-tomcat-9.0.39.tar.gz’ saved [11282879/11282879]

Then, decompress it and rename the folder.

:~# tar -xzvf apache-tomcat-9.0.39.tar.gz
:~# mv apache-tomcat-9.0.39 tomcat

After that, you need to change the owner of the folder and assign the required permissions so that it can run smoothly. Remember that now, we are using the root user.

:~# chown -R tomcat:tomcat /opt/tomcat/
:~# chmod +x /opt/tomcat/bin/*

Now, on the .bashrc file add the CATALINA_HOME path.

:~# nano ~/.bashrc
export CATALINA_HOME=/opt/tomcat

Save the changes and close the file.

Then, refresh bash.

:~# source ~/.bashrc

After that, we can run Apache Tomcat. To do it, just type this command:

:~# /opt/tomcat/bin/startup.sh

Next, open your web browser ad go http://your-server:8080. And you will see this.

If you want to set a password to improve security of the manager web app. So, open the tomcat-users.xml

:~# nano /opt/tomcat/conf/tomcat-users.xml

In the tomcat-user section, you have to add the username and password.

<role rolename="manager-gui"/>
<user username="XXXXXX" password="XXXXXXX" roles="manager-gui,admin-gui"/>

Of course, replace the password for yours.

Then, restart Tomcat.

:~# ./shutdown.sh
:~# ./startup.sh

And go to the web browser again. Next, refresh the page. And that is it.

Conclusion

Apache Tomcat is the best solution to deploy and serve web applications made with Java. So if you program in Java, you should learn how to manipulate Tomcat. As you have learned in this post, it is not very complex to learn how to install it in  Ubuntu 20.04 / Debian 10.

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The post How to install Apache Tomcat on Ubuntu 20.04 / Debian 10? appeared first on Linux Windows and android Tutorials.

One of the biggest strengths of CentOS is that it has a wide range of packages and programs that can be installed. On the other hand, the CentOS project has many communities and official repositories that extend even more the functionality of the distribution.

OpenJDK or Oracle Java

Since Java version 11, the license has changed and become a little more restrictive for commercial purposes. However, OpenJDK continues to run alongside the commercial version that includes professional support.

The above situation opens a small controversy about which implementation to use. And the answer depends on each developer however, with OpenJDK you will not have license problems and is ideal for testing features and educational projects.

Well, for this tutorial I will choose OpenJDK. Do not worry it is Java but open source.

Let’s go for it.

Install Java 15 on CentOS 8 / Centos 7

Java 15 is available as an RPM package from the Oracle website. So you can go to the download section and download the RPM package corresponding to your processor architecture.

However, using the terminal and wget command is faster and even easier.

So, open the terminal or start an SSH session and type the following command.

wget --no-check-certificate -c --header "Cookie: oraclelicense=accept-securebackup-cookie" https://download.oracle.com/otn-pub/java/jdk/15+36/779bf45e88a44cbd9ea6621d33e33db1/jdk-15_linux-x64_bin.rpm

And it will automatically start the download.

You can then install the package locally with DNF.

sudo dnf localinstall jdk-15_linux-x64_bin.rpm
Failed to set locale, defaulting to C.UTF-8
Last metadata expiration check: 0:01:51 ago on Wed Sep 23 11:22:58 2020.
Dependencies resolved.
Package Architecture Version Repository Size
Installing:
jdk-15 x86_64 2000:15-ga @commandline 162 M
Transaction Summary
Install 1 Package
Total size: 162 M
Installed size: 314 M
Is this ok [y/N]

Once the installation is complete, if you have several versions of Java you can choose the default by running the following command:

sudo alternatives --config java
There is 1 program that provides 'java'.
Selection Command
*+ 1 /usr/java/jdk-15/bin/java
Enter to keep the current selection[+], or type selection number:

Although in my case I only have this installation.

Finally, check the JAva version to see if the command works correctly:

java --version
java version "15" 2020-09-15
Java(TM) SE Runtime Environment (build 15+36-1562)
Java HotSpot(TM) 64-Bit Server VM (build 15+36-1562, mixed mode, sharing)

So, enjoy it.

Conclusion

Java is an old rocker who has a lot to contribute. So it is not surprising that he is a valued Oracle and has very active development. Now with version 15, you can enjoy attractive new features.

So, enjoy it. Share this post and join our Telegram Channel.

The post How to install Java 15 on CentOS 8 / CentOS 7 appeared first on Linux Windows and android Tutorials.

One of the biggest strengths of OpenSUSE is that it has a wide range of packages and programs that can be installed. On the other hand, the OpenSUSE project has many community and official repositories that extend even more the functionality of the distribution.

OpenJDK or Oracle Java

Since Java version 11, the license has changed and become a little more restrictive for commercial purposes. However, OpenJDK continues to run alongside the commercial version that includes professional support.

The above situation opens a small controversy about which implementation to use. And the answer depends on each developer however, with OpenJDK you will not have license problems and is ideal for testing features and educational projects.

Well, for this tutorial I will choose OpenJDK. Do not worry it is Java but open source.

Let’s go for it.

Install Java 15 on OpenSUSE 15.2

Once you have a terminal session open, it is necessary to completely upgrade your system. To do this, run the following command:

:~$ sudo zypper up

Once the system upgrade is complete, we can continue.

Java 15 packages can be found in an OpenSUSE factory repository. This repository has proven to be quite stable and we will be able to use it without problems.

So to add this repository run it:

:~$ sudo zypper ar http://download.opensuse.org/repositories/Java:/Factory/openSUSE_Leap_15.2/ java

Now that the repository has been added, it needs to be reprioritized so that it does not get into trouble with the rest:

:~$ sudo zypper mr -p 70 java
Repository 'java' priority has been set to 70.

Then, refresh all the repositories to load the newly added one. When you first use this repository, you will be asked to accept the GPG key for it.

:~$ sudo zypper refresh
Retrieving repository 'java' metadata --------------------------------------------------------------------------------------------------------------------------------[|]
 New repository or package signing key received:
 Repository:       java                                        
   Key Name:         Java OBS Project Java@build.opensuse.org  
   Key Fingerprint:  97119219 72E27C87 BBC1BA89 E38C29BC 4276E0B9
   Key Created:      Mon 18 Jun 2018 09:42:22 AM -04             
   Key Expires:      Wed 26 Aug 2020 09:42:22 AM -04             
   Rpm Name:         gpg-pubkey-4276e0b9-5b27b6be                
 Do you want to reject the key, trust temporarily, or trust always? r/t/a/?: a
 Retrieving repository 'java' metadata ……………………………………………………………………………………………………………..[done]
 Building repository 'java' cache ………………………………………………………………………………………………………………….[done]
 Repository 'Non-OSS Repository' is up to date.                                                                                                                           
 Repository 'Main Repository' is up to date.                                                                                                                              
 Retrieving repository 'Main Update Repository' metadata ……………………………………………………………………………………………..[done]
 Building repository 'Main Update Repository' cache ………………………………………………………………………………………………….[done]
 Retrieving repository 'Update Repository (Non-Oss)' metadata …………………………………………………………………………………………[done]
 Building repository 'Update Repository (Non-Oss)' cache ……………………………………………………………………………………………..[done]
 All repositories have been refreshed.

Now, you can install Java 15 on OpenSUSE 15.2

:~$ sudo zypper in java-15-openjdk

Finally, check the installed version

:~$ java --version
openjdk 15-internal 2020-09-15
OpenJDK Runtime Environment (build 15-internal+33-suse-lp152.14.15-x8664)
OpenJDK 64-Bit Server VM (build 15-internal+33-suse-lp152.14.15-x8664, mixed mode)

So, enjoy it.

Conclusion

Java 15 is an improved version of a great programming language. This makes many developers attentive to its evolution with a view to a new LTS version. Now you know how to install it in OpenSUSE 15.2 which is a distribution quite focused on newcomers but also professional developers. So, you know how to install Java 15 on OpenSUSE 15.2

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Thanks for reading the post.

The post How to install Java 15 on OpenSUSE 15.2? appeared first on Linux Windows and android Tutorials.

Gradle is an open-source build automation tool used for Java, Groovy, and Scala development. Basically, it builds upon the concepts of Apache Ant & Apache Maven. Gradle uses Groovy instead of XML for declaring the project configuration. Groovy is a dynamic, object-oriented programming language to define the project configurations.

So, let us start.

Installing Gradle on Ubuntu 20.04

Gradle is important for the effective development of Java applications. So the first requirement is to install Java on Ubuntu 20.04.

So, open a terminal and install it using the following command:

:~$ sudo apt install openjdk-11-jre
Reading package lists… Done
Building dependency tree
Reading state information… Done
The following additional packages will be installed:
at-spi2-core ca-certificates-java fonts-dejavu-extra java-common libatk-bridge2.0-0 libatk-wrapper-java libatk-wrapper-java-jni libatk1.0-0 libatk1.0-data
libatspi2.0-0 libavahi-client3 libavahi-common-data libavahi-common3 libcups2 libdrm-amdgpu1 libdrm-intel1 libdrm-nouveau2 libdrm-radeon1 libfontenc1 libgif7 libgl1
libgl1-mesa-dri libglapi-mesa libglvnd0 libglx-mesa0 libglx0 libice6 liblcms2-2 libllvm10 libnspr4 libnss3 libpciaccess0 libpcsclite1 libsensors-config libsensors5
libsm6 libvulkan1 libwayland-client0 libx11-xcb1 libxaw7 libxcb-dri2-0 libxcb-dri3-0 libxcb-glx0 libxcb-present0 libxcb-randr0 libxcb-shape0 libxcb-sync1
libxcomposite1 libxdamage1 libxfixes3 libxft2 libxi6 libxinerama1 libxkbfile1 libxmu6 libxrandr2 libxrender1 libxshmfence1 libxt6 libxtst6 libxv1 libxxf86dga1
libxxf86vm1 mesa-vulkan-drivers openjdk-11-jre-headless x11-common x11-utils
Suggested packages:
default-jre cups-common liblcms2-utils pcscd lm-sensors libnss-mdns fonts-ipafont-gothic fonts-ipafont-mincho fonts-wqy-microhei | fonts-wqy-zenhei fonts-indic
mesa-utils
The following NEW packages will be installed:
at-spi2-core ca-certificates-java fonts-dejavu-extra java-common libatk-bridge2.0-0 libatk-wrapper-java libatk-wrapper-java-jni libatk1.0-0 libatk1.0-data
libatspi2.0-0 libavahi-client3 libavahi-common-data libavahi-common3 libcups2 libdrm-amdgpu1 libdrm-intel1 libdrm-nouveau2 libdrm-radeon1 libfontenc1 libgif7 libgl1
libgl1-mesa-dri libglapi-mesa libglvnd0 libglx-mesa0 libglx0 libice6 liblcms2-2 libllvm10 libnspr4 libnss3 libpciaccess0 libpcsclite1 libsensors-config libsensors5
libsm6 libvulkan1 libwayland-client0 libx11-xcb1 libxaw7 libxcb-dri2-0 libxcb-dri3-0 libxcb-glx0 libxcb-present0 libxcb-randr0 libxcb-shape0 libxcb-sync1
libxcomposite1 libxdamage1 libxfixes3 libxft2 libxi6 libxinerama1 libxkbfile1 libxmu6 libxrandr2 libxrender1 libxshmfence1 libxt6 libxtst6 libxv1 libxxf86dga1
libxxf86vm1 mesa-vulkan-drivers openjdk-11-jre openjdk-11-jre-headless x11-common x11-utils
0 upgraded, 68 newly installed, 0 to remove and 86 not upgraded.
Need to get 71.3 MB of archives.
After this operation, 555 MB of additional disk space will be used.
Do you want to continue? [Y/n]

Once you have entered your password, the installation will begin.

When the installation is finished, you can check the version of Java installed:

:~$ java --version
openjdk 11.0.8 2020-07-14
OpenJDK Runtime Environment (build 11.0.8+10-post-Ubuntu-0ubuntu120.04)
OpenJDK 64-Bit Server VM (build 11.0.8+10-post-Ubuntu-0ubuntu120.04, mixed mode, sharing)

This indicates that Java is ready for action.

Downloading and installing Gradle on Ubuntu 20.04

Now the next step is to download and install Gradle. To do this, go to the /tmp/ folder and use the wget command to download:

:~$ wget -c https://services.gradle.org/distributions/gradle-6.5.1-bin.zip
--2020-08-02 19:24:17-- https://services.gradle.org/distributions/gradle-6.5.1-bin.zip
Resolving services.gradle.org (services.gradle.org)… 104.18.191.9, 104.18.190.9, 2606:4700::6812:bf09, …
Connecting to services.gradle.org (services.gradle.org)|104.18.191.9|:443… connected.
HTTP request sent, awaiting response… 301 Moved Permanently
Location: https://downloads.gradle-dn.com/distributions/gradle-6.5.1-bin.zip [following]
--2020-08-02 19:24:18-- https://downloads.gradle-dn.com/distributions/gradle-6.5.1-bin.zip
Resolving downloads.gradle-dn.com (downloads.gradle-dn.com)… 104.17.160.20, 104.17.159.20, 2606:4700::6811:9f14, …
Connecting to downloads.gradle-dn.com (downloads.gradle-dn.com)|104.17.160.20|:443… connected.
HTTP request sent, awaiting response… 200 OK
Length: 102367135 (98M) [application/zip]
Saving to: ‘gradle-6.5.1-bin.zip’
gradle-6.5.1-bin.zip 100%[=====================================================================================>] 97.62M 841KB/s in 2m 2s
2020-08-02 19:26:21 (821 KB/s) - ‘gradle-6.5.1-bin.zip’ saved [102367135/102367135]

At the time of writing this post, the latest stable version of Gradle is 6.5.1 So, check first which is the latest version and modify the command.

If you don’t have the unzip command installed, do it because we will need it.

sudo apt install unzip

Now unzip the downloaded file into a directory like /opt/ where it will remain indefinitely:

:~$ sudo unzip -d /opt/gradle gradle-6.5.1-bin.zip

The next step is to make Gradle available from anywhere in the terminal. Also, make it available to all users.

To do this, create a new file called gradle.sh in /etc/profile.d/

:~$ sudo nano /etc/profile.d/gradle.sh

And add the following content:

export GRADLE_HOME=/opt/gradle/gradle-6.5.1
export PATH=${GRADLE_HOME}/bin:${PATH}

Save the changes, and close the editor.

Assign execution permissions to the file:

:~$ sudo chmod +x /etc/profile.d/gradle.sh

And finally, source the file to apply the changes:

:~$ source /etc/profile.d/gradle.sh

Now you can use Gradle from the terminal. So, check the installation, showing the version of the program:

:~$ gradle -v
Welcome to Gradle 6.5.1!
Here are the highlights of this release:
Experimental file-system watching
Improved version ordering
New samples
For more details see https://docs.gradle.org/6.5.1/release-notes.html

Gradle 6.5.1
Build time: 2020-06-30 06:32:47 UTC
Revision: 66bc713f7169626a7f0134bf452abde51550ea0a
Kotlin: 1.3.72
Groovy: 2.5.11
Ant: Apache Ant(TM) version 1.10.7 compiled on September 1 2019
JVM: 11.0.8 (Ubuntu 11.0.8+10-post-Ubuntu-0ubuntu120.04)
OS: Linux 5.4.0-33-generic amd64

So, enjoy it. Gradle is installed and ready to start work.

Conclusion

Gradle is a tool for the development of Java applications. So, thanks to this post, you have learned how to install it in a system like Ubuntu 20.04 that is so popular among Java developers.

So, share this post, and join our Telegram Channel.

The post How to install Gradle on Ubuntu 20.04? appeared first on Linux Windows and android Tutorials.