I’m learning Java. To read JSON in my application, I downloaded this JSON library; which is an automatic module. I included that library in my module descriptor like: My settings.json in vscode: How do I include the jar file in my module and import it into my Java file? Screenshot: Answer TL;DR — As thi…
Tag: java-11
Eclipse(2020 09) Java Installation issue || Windows 10 OS
I am new to Java programming. I have installed Java SE 11 (LTS) (JDK 11.0.8) on my OS. Note that former Java also has jre folder in it. But Java 11 onward there come only JDK folder. So, I have set JAVA_HOME environment variable as well as, included jdkbin in path as well. By checking on cmd java version show…
LocalDate.parse results in “DateTimeParseException…could not be parsed: null”
I am attempting to parse a date time stamp and extract only the date. Like so: But this results in the following Exception: This seems related to this issue: https://bugs.openjdk.java.net/browse/JDK-8226704. But the line numbers in my stack do not match up with those in the issue. Appreciate any pointers on w…
Where is the description of Constant Folding in the Java Language Specification, Java SE 11 Edition (JLS SE 11)?
As far as I know, Java deals with constant variables §4.12.4 by constant folding in compile time. I’ve tried my best, but I couldn’t find its description from JLS. Could anybody tell me where I could find official description of the constant folding process for Java 11? Answer The specification do…
What is Coder in String Value?
I am reading a CSV file, by using com.opencsv.CSVReader Like below Value for header is coming like below screen shot: What’s coder here (Highlighted in yellow)? Why the value is 1 for first index and 0 for all other? Answer The official response is “none of your business”, since it’s a…
Keycloak java.lang.NoClassDefFoundError: java/security/acl/Group using Springboot
So we are building a Springboot back-end with Keycloak integration. But we get the following error when running the back-end on a docker swarm service: I tried it with JDK 8 and JDK 11 since the following post implies that the wrong JDK can cause a problem: Stackoverflow post. It still gives this error. The f…
Lucene LongPoint Range search doesn’t work
I am using Lucene 8.2.0 in Java 11. I am trying to index a Long value so that I can filter by it using a range query, for example like so: +my_range_field:[1 TO 200]. However, any variant of that, even my_range_field:[* TO *], returns 0 results in this minimal example. As soon as I remove the + from it to
Getting ‘allocation stall’ when enabling ZGC
I am testing the new zgc garbage collector that was included in java 11 since it promises really low latency. Our application is a real-time service that creates and destroys many objects per second and it does it in a multi-threaded environment using akka. When enabling zgc by passing the options -XX:+Unlock…
Can’t connect to kubernetes API from inside the cluster
I’m trying to use the fabric8io/kubernetes-client in a simple example on my local minikube cluster where I get an IP of a pod some-pod-name-jnfen3 is a name of a pod which finished execution and visible if I execute kubectl get pods. https://localhost:32780/ is a kubernetes API host which I get from kub…
parallelStream() java 1.8 vs 11
Consider the following code: When it is compiled and run with java 11, it returns the following: But with java 1.8, it returns different result: Why results are different? Answer Both results are consistent with the Java Memory Model. One possible ordering in which execution occurs is: but, because you don…