Is there any way to define a sum type in Java? Java seems to naturally support product types directly, and I thought enums might allow it to support sum types, and inheritance looks like maybe it could do it, but there is at least one case I can’t resolve. To elaborate, a sum type is a type which can ha…
JAVA ERROR : package com.sun.rowset is not visible : com.sun.rowset is declared in module java.sql.rowset, which does not export it
I’m simply try to run this code: When I run it I get: Error:(1, 15) java: package com.sun.rowset is not visible (package com.sun.rowset is declared in module java.sql.rowset, which does not export it) I’m using IntelliJ and I tried to import rs2xml.jar, and that still doesnt help. Answer As of Jav…
Spring Test cannot get Spring Configuration Beans
I also tried putting EnvironmentServiceTestConfiguration as a non-inner non-static class, but didn’t help. Here is what I tried in a separate class: didn’t work either The test class is located in test/java/com.bhavya.test package. I am trying to run this particular test test1 This is my first tes…
IdentitySet / IdentityHashSet (use IdentityHashMap)
I know about IdentityHashMap, but I need to use to something like “IdentitySet” (use equals as o1 == o2 ). I’m going to use one to listen Observable list with “extractor” (JavaFX): …
How to solve the java.nio.file.NoSuchFileException?
I have a file called “result.csv”, from that file i want to read certain data and display them. I have that file in my eclipse project folder itself. Still i’m unable to read the file. OUTPUT: Can anyone point where exactly i missed? and how can i overcome this or any alternate methods for t…
TextView Numbers shown in English in Persian font
I am loading a string which contains some number (all in Persian) into an android TextView. Everything was fine until I changed my custom font, numbers of text shown as English number. Expected : …
Temporarily stop consuming RabbitMQ messages and resume later
I use Java’s rabbitmq-client (https://mvnrepository.com/artifact/com.rabbitmq/amqp-client) and I need to implement the following scenario: While receiving Rabbit messages, I may need to pause Rabbitmq consumption from particular queues if I suspect that all awaiting data will not fit in memory. After I …
Transform SQL to Hibernate criteria
I am writing a method for retrieving clients with sum of their orders (order.total) higher and less than input values. All its okay, but, sometimes i am get an error: How can i correcting this method, or, maybe, convert this in full criteria style? Answer In the end, i solved this problem by this way, using s…
Creating two objects with same name in Java
I have a class name Planet and I am making objects in main. However, I saw my instructor doing this: So basically, my instructor is also creating two objects. I understand that a new object is basically formed when constructor is called but I always thought that the two objects need to have distinct names as …
What does “class loading deadlock” mean here?
I have this classes: And code inspector is detecting this warning: Referencing subclass NonRegisteredUser from superclass User initializer might lead to class loading deadlock What does it mean exactly? Answer The deadlock can only occur if you have 2 threads and one starts to load User and one starts to load…