How Do You Invoke the main Section of a Groovy Program?

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Problem scenario
Your Groovy code has a section like this:

class Example {
static void main(String[] args) {
…

But this section above is not executing when you run your Groovy program. There are no errors however. How do you get it to execute?

Possible Solution #1
Remove lines of code (or statements) that are outside the “class Example {…”

Possible Solution #2
See this posting: How Do You Invoke a Class in a Groovy Program?

…

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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 Quickly Add a New Event to the Windows Logs Using PowerShell?

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Problem scenario
You like adding logging messages manually in Linux/Unix. You do it from the command prompt with “# write a cool message here”. You review the messages with a “history” command. You also append messages to log files in /var/log/foorbar.d with ‘echo “note this” ‘. How do you introduce your own messages into Windows event log?

Solution
Run a command like this but change “Application” to “Security” or whichever log category you want:

Write-EventLog -LogName Application -EventId 3 -Message “Continual Integration helps!” -Source “Windows Error Reporting”

# Note that “Windows Error Reporting” is just one of several valid sources. …

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How Do You Troubleshoot the Message “ImportError: cannot import name ‘pubsub_v1′”?

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Problem scenario
From the Python command prompt or when running a Python program, you receive this message “ImportError: cannot import name ‘pubsub_v1′”. What should you do?

Solution
Possible Solution #1
Try to run the program as sudo: sudo python nameOfProg.py

Possible Solution #2
Prerequisite
This assumes that pip has been installed.

…

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How Do You Troubleshoot the Message “ImportError: No module named ‘google'”?

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Problem scenario
From the Python command prompt or when running a Python program, you receive this message “ImportError: No module named ‘google'”. What should you do?

Solution
Possible Solution #1
Try to run the program as sudo: sudo python nameOfProg.py

Possible Solution #2
Prerequisite
This assumes that pip has been installed.

…

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How Do You use the Built-in Exception Handling Functionality of Python?

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Problem scenario
You want to use the built-in exception handling in your Python program. You know some part or parts of the code may throw an error. How do you use the “except” keyword?

Solution
Use the “try” key word. Here is an example of a program that throws an error:

commandthatdoesnotexist
x = 1 + 1
print(x)

python3 progwitherror.py
Traceback (most recent call last):
File “progwitherror.py”,

…

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How Do You Write a Python Program to Show the Status of the Servers in AWS?

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Problem scenario
You want to list the statuses of each EC-2 instance in AWS using Python. How do you do this for a given region in AWS (e.g., us-west-1)?

Solution
Prerequisites
This assumes you have installed Boto3. If you do not know how, see this posting “How do you install Boto 3 on a RHEL server in AWS?

…

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How Do You Troubleshoot an Error like This in Groovy “groovy.lang.MissingMethodException”?

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Problem scenario
You run a Groovy program like this: groovy foobar.groovy

You see this message:

Caught: groovy.lang.MissingMethodException: No signature of method: java.lang.Boolean.call() is applicable for argument types: (foobar$_run_closure5$_closure6) values: [foobar$_run_closure5$_closure6@6150c3ec]
Possible solutions: wait(), any(), wait(long), and(java.lang.Boolean), each(groovy.lang.Closure), any(groovy.lang.Closure)
groovy.lang.MissingMethodException: No signature of method: java.lang.Boolean.call() is applicable for argument types: (foobar$_run_closure5$_closure6) values: [foobar$_run_closure5$_closure6@6150c3ec]
Possible solutions: wait(), any(), wait(long), and(java.lang.Boolean), each(groovy.lang.Closure), any(groovy.lang.Closure)
at foobar$_run_closure5.doCall(foobar.groovy:56)

What should you do?

…

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