diff between SoftReference and WeakReference

A complete answer can be found at: https://stackoverflow.com/questions/299659/whats-the-difference-between-softreference-and-weakreference-in-java

From Understanding Weak References, by Ethan Nicholas:

Weak references
A weak reference, simply put, is a reference that isn't strong enough to force an object to remain in memory. Weak references allow you to leverage the garbage collector's ability to determine reachability for you, so you don't have to do it yourself. You create a weak reference like this:

WeakReference weakWidget = new WeakReference(widget);

and then elsewhere in the code you can use weakWidget.get() to get the actual Widget object. Of course the weak reference isn't strong enough to prevent garbage collection, so you may find (if there are no strong references to the widget) that weakWidget.get() suddenly starts returning null.
...
Soft references
A soft reference is exactly like a weak reference, except that it is less eager to throw away the object to which it refers. An object which is only weakly reachable (the strongest references to it are WeakReferences) will be discarded at the next garbage collection cycle, but an object which is softly reachable will generally stick around for a while.
SoftReferences aren't required to behave any differently than WeakReferences, but in practice softly reachable objects are generally retained as long as memory is in plentiful supply. This makes them an excellent foundation for a cache, such as the image cache described above, since you can let the garbage collector worry about both how reachable the objects are (a strongly reachable object will never be removed from the cache) and how badly it needs the memory they are consuming.

And Peter Kessler added in a comment:

The Sun JRE does treat SoftReferences differently from WeakReferences. We attempt to hold on to object referenced by a SoftReference if there isn't pressure on the available memory. One detail: the policy for the "-client" and "-server" JRE's are different: the -client JRE tries to keep your footprint small by preferring to clear SoftReferences rather than expand the heap, whereas the -server JRE tries to keep your performance high by preferring to expand the heap (if possible) rather than clear SoftReferences. One size does not fit all.

Sonarqube cheat sheet

SonarQube Best open source static analyzer.
(IMHO :-) ).

1.
How to create custom plugins for Sonar

https://devwebcl.blogspot.com/2018/10/custom-sonarqube-plugins-63.html

2.
default port: 9000
http://127.0.0.1:9000/

http://localhost:9000/

3.
Maven command line:

mvn sonar:sonar -Dsonar.host.url=http://127.0.0.1:9000 -Dsonar.login=d676f79d8ba83cdcf69f38f8471f0284ee242e09

4.
Quality Gates

Quality Gates are the best way to ensure that standards are met and regulated across all the projects in your organization. Quality Gates can be defined as a set of threshold measures set on your project like Code Coverage, Technical Debt Measure, Number of Blocker/Critical issues, Security Rating, etc.

5.
Quality Profiles

A quality profile in Sonar consists of: A set of activated coding rules among +600 available (PMD, Checkstyle and FindBugs): an activation level (mandatory or optional) and parametrization for each rule.

6.
wsdl jar
to be tested jar wsdl client proxies :

           
                      <plugin>
                <groupId>org.jvnet.jax-ws-commons</groupId>
                <artifactId>jaxws-maven-plugin</artifactId>
                <version>2.3</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>wsimport</goal>
                        </goals>
                        <configuration>
                            <wsdlDirectory>${basedir}/src/main/resources/wsdl/</wsdlDirectory>
                            <wsdlLocation>wsdl/endpoint_sample_wsdl.wsdl</wsdlLocation>

                            <sourceDestDir>${basedir}/src/main/java</sourceDestDir>

7. sonnar-scanner cli

sonar-scanner -Dsonar.projectKey=my-best-project

8. sonar-project.properties
to active a project and be used by sonar cli.
Create an user and generate token, then add to properties file:

# must be unique in a given SonarQube instance
sonar.projectKey=my:project
sonar.login=f86a58b7f520bfc6bbdb5bf03a0671ce64860f0c
sonar.java.binaries=target
 

#to avoid java parsing
sonar.exclusions=**/*.java

9. important not default rules

- https://rules.sonarsource.com/java/RSPEC-3749
  Members of Spring components should be injected

- https://rules.sonarsource.com/java/RSPEC-4288
  Spring components should use constructor injection