Quiz yourself: Controlling the number of instances of a class

Which is the best approach: singletons, sealed classes, abstract classes, final classes, or enums?Imagine that your design requires exactly four instances of a particular class.Which approach best provides for this need? Choose one.A. Singletons B. Sealed classes C. Abstract classes D. Final classes E. Enums Answer. Option A is incorrect...

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The arrival of Java 17!

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Oracle is proud to announce the general availabilty of JDK 17. This release is the eighth Feature Release delivered on time through the six-month release cadence. This level of predictability allows developers to easily manage their adoption of innovation thanks to s steady stream of expected changes.Java’s ability...

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Quiz yourself: Creating records within a Java sealed-type hierarchy

A record type is always implicitly final, so it cannot be extended by either a regular class or a record.You’re designing an IoT device controlled by Java. The device has two modes, one for day and one for night. The modes differ in terms of configuration data, and...

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Declarative and Immutable Pipeline of Transformations

A few months ago I made a small Java library, which is worth explaining since the design of its classes and interfaces is pretty unusual. It’s very much object-oriented for a pretty imperative task: building a pipeline of document transformations. The goal was to do this in a...

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Developers disassemble! Use Java and hsdis to see it all.

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Use the HotSpot Disassembler to see what’s happening to your code.Figure 1 below is what you might see when you ask your Java Virtual Machine (JVM) to show you the output of a just-in-time (JIT) compilation performed by the HotSpot JVM after it optimized your program to take...

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