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Maven cheatsheet

June 4, 2021 by louie171

Just a place for me to store handy bits and pieces. Having not used it for awhile to remind of things, I’ll likely to forget ! How to compile to different versions of Java ( see also https://mkyong.com/maven/maven-error-invalid-target-release-1-11/ )

			<plugin>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.8.1</version>
				<configuration>
					<source>11</source>
					<target>11</target>
				</configuration>
			</plugin>

<artifactId>maven-compiler-plugin</artifactId>

</configuration>

</plugin>

In the <build> section How to change the output/target dir Handy if you want to … Read more

Running Docker on AWS

June 17, 2021April 27, 2021 by louie171

Recently I wanted to use my Java Tomcat Docker image on AWS to run a spring boot app. I looked at the various ways of setting this up ECS (Elastic Container), and found it to be a load of hassle ( for what I needed , I don’t need Kubernetes style functionality , just a … Read more

Threads in Java

April 12, 2021April 9, 2021 by louie171

We need to control access to shared state ( when multiple threads are at work ), to avoid unexpected results. In the case of the program below the shared state is the int sheepCount. 10 different threads call the method incrementAndReport() . Without thread management

public class Ch18SheepManager {

	  private int sheepCount = 0;

	  private void incrementAndReport() {

		    Thread t = Thread.currentThread();		    
		    System.out.print("sheepcount = " + (++sheepCount) + "	Worker    - " + t.getName());										

	  }

	  public static void main(String[] args) throws Exception {
		
		    var service = Executors.newFixedThreadPool(20);
		    var manager = new Ch18SheepManager();

		    for (int i = 0; i < 10; i++)
			     service.submit(() -> manager.incrementAndReport());
		
	  }

}

public class Ch18SheepManager {

private int sheepCount = 0;

private void incrementAndReport() {

Thread t = Thread.currentThread();

System.out.print("sheepcount = " + (++sheepCount) + " Worker - " + t.getName());

}

public static void main(String[] args) throws Exception {

var service = Executors.newFixedThreadPool(20);

var manager = new Ch18SheepManager();

for (int i = 0; i < 10; i++)

service.submit(() -> manager.incrementAndReport());

}

Output ( wonky ) Every thread is trying to … Read more

Creating drop downs (that don’t alter the space below them when opened )

March 14, 2021 by louie171

Just a very quick tutorial on how to create a dropdown (like a drop down menu), so that when you expand the dropdown the space below it isn’t pushed down. Like this (all the Other actions below contain a drop down menu – see next image) When I expand one of the menus I … Read more

css rotate ( from a certain point )

March 10, 2021March 8, 2021 by louie171

Just a quick note on how this works. I wanted to stick a div against the right of the page ( with abit of fixed positioning ), then rotate it so it was 90 degrees (sitting nice and flush against the right). But when I did it ( just with rotate it rotates about the … Read more

How Lambdas can be useful in Java

April 22, 2021February 18, 2021 by louie171

I’m revising for the OCP (Oracle Certified Professional Java Programmer ), and running over Lambdas at the moment. In tutorials I see many of them seem to focus on what they are , what they do , streams etc. Not much on how they can be used to improve code ( and making less Class … Read more