Java Questions
Sealed Class Sealed classes in Java allow inheritance from the known sub classes that are specified by the permits keyword or defined in the same class file. If we mark a class as sealed it should have some sub classes specified using the permits clause or sub classes defined in the file. For example public […]
Differences between JDBC and ODBC Databases store your app’s data, but your program needs a safe, standard way to talk to them. Two popular technologies enable this: JDBC (for Java) and ODBC (language-neutral). Think of them as “interpreters” that translate your program’s requests (like “fetch all users”) into something a database understands. JDBC JDBC (Java […]
What are the new features in JDK15 Some of the interesting new features in JDK15 are as follows: Sealed Class Sealed Interfaces Text Blocks Records Hidden Classes Sealed Class https://www.testingdocs.com/questions/what-are-sealed-classes-in-java/ Sealed Interface https://www.testingdocs.com/questions/what-is-a-sealed-interface-in-java/ Text Blocks Textblocks are designed to support multi-line strings in the Java code. Text block begins with three double quotes and newline. […]
How to Download and Install Oracle JDK 14 On this page, let’s see detailed steps to install Oracle 14 JDK on Windows 10 operating system. How to change the install directory and to see JDK documentation. Download Pick the JDK installer to download Download the 64-bit installer. Download the .exe file […]
How to fix: log4j:WARN No appenders could be found for logger The warning message log4j:WARN No appenders could be found for logger (LoggerExample) indicates that Log4j is unable to find any appenders configured for the LoggerExample logger. This issue can occur for a variety of reasons, but it typically means that either the log4j.xml configuration […]
How to Fix JUnit Invalid test class Error Exception Trace org.junit.runners.model.InvalidTestClassError: Invalid test class ‘com.testingdocs.tutorials.TestCaseOne’: 1. The class com.testingdocs.tutorials.TestCaseOne is not public. 2. Test class should have exactly one public constructor at org.junit.runners.ParentRunner.validate(ParentRunner.java:525) at org.junit.runners.ParentRunner.<init>(ParentRunner.java:102) at org.junit.runners.BlockJUnit4ClassRunner.<init>(BlockJUnit4ClassRunner.java:84) at org.junit.runners.JUnit4.<init>(JUnit4.java:23) The error message suggests that your JUnit test class has incorrect visibility or constructor issues. […]