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Java Concurrency With Project Loom

Early Access: Java Concurrency With Project Loom

I am excited about Project Loom. The project focuses on easy to use lightweight concurrency for the JavaVM. Nowadays, the JavaVM provides a one java thread to one OS thread model to the programmer. While it's actually the current Oracle implementation, it used to be that many JavaVM versions ago, threads provided to the programmer were actually green threads.

Project Loom goes down that road again, providing lightweight threads to the programmer. Those lightweight threads are mapped to OS threads in a "many-to-many" relationship. 

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Java Concurrency Evolution

Since the early days of Java, Threads were available to support concurrent programming. Interestingly till Java 1.1, green threads (virtual threads) were supported by the JVM, but they were dropped in favor of native OS threads, however with Project Loom on the horizon (targeted for Java 16 or later?), virtual threads are on track to become mainstream again.

The goal of this article is to go through the main milestones for the evolution of thread/concurrency handling in Java. As the topic can easily fill a library full of books, the following aspects are out of scope (basically, the goal is to take a look at the happy path of Java concurrency):