How Do You Install Java so You Can Compile Programs on a RHEL Server?

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Problem scenario
You have installed Java. But you cannot use the javac command. You get errors like this: “-bash: javac: command not found”

How do you install Java so you can compile programs on a RedHat Linux server?

Solution
Run this command: sudo yum -y install java-devel

If you want to do this on a Debian or Ubuntu Linux server,

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How Do You Install and Configure the rdf4j Server and Workbench GUI?

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Problem scenario
You want to use the rdf4j (Resource Description Framework for Java). You want to install the rdf4j server and workbench. You are using Debian 9 Linux. What should you do?

Solution
Prerequisites
i. We recommend having a 30 GB of hard disk free.

ii. We recommend having 5.75 GB of RAM (it can be a combination of RAM and swap space).

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How Do You Find the Version of Java that is Installed on Your Windows Server?

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Problem scenario
You want determine what version of Java is installed (if any). What do you do?

Solution
Open PowerShell and run this command:
(Get-WmiObject Win32_Product | Where {$_.Name -match “Java”}).Version

Alternative way without PowerShell:
1. Go to Control Panel -Uninstall a Program
2. See if Java is installed

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How Do You Troubleshoot the Java Program Message “java.sql.SQLException: No database selected”

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Problem scenario
Your Java program returns this message: “java.sql.SQLException: No database selected”
What should you do?

Possible Solution #1
Your SQL statement was appropriate for a database but not for the circumstance of connecting to a SQL instance. Try show databases; instead of the SQL you were running.

Possible Solution #2
Did you connect to the SQL instance you thought you connected to?

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How Do You Run a Java Program to Run SQL Commands Against a MySQL Database?

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Problem scenario
You have a MySQL database. Rather than use a SQL front-end application, you want to write a Java program that will run a SQL statement against the database. What should you do?

Solution

1. Install the Java compiler if it is not already installed. If you need assistance, see this posting.

2. Run this command:
curl -Lk https://www.javatpoint.com/src/jdbc/mysql-connector.jar >

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How Do You Troubleshoot the Java Program Message “com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: Unknown database foobar”?

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Problem scenario
Your Java program returns this message: “com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: Unknown database foobar”

What should you do?

Possible solution #1
Are you using Amazon Aurora? AWS has a MySQL PaaS offering. You may have a section of the Java code that looks like this:

Connection con=DriverManager.getConnection(“jdbc:mysql://foobar-us-west-2b.abcdefghijk.us-west-2.rds.amazonaws.com:3306/foobar”)

Remove the last “foobar” from the end. The connection string should look like this for Aurora databases:

jdbc:mysql://foobar-us-west-2b.abcdefghijk.us-west-2.rds.amazonaws.com:3306/foobar

Recompile the program.

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How Do You Troubleshoot the Message “Error: Config file not found: /usr/lib/jvm/java-9-openjdk-amd64/conf/management/management.properties”?

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Problem scenario
You are trying to run Apache Zookeeper or some other application. You enounter the problem Error: Config file not found: /usr/lib/jvm/java-9-openjdk-amd64/conf/management/management.properties. What should you do?

Possible solution
This is a workaround. Run these commands:
sudo mkdir -p /usr/lib/jvm/java-9-openjdk-amd64/conf/management/
sudo touch /usr/lib/jvm/java-9-openjdk-amd64/conf/management/management.properties

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