Garbage Collection in Java

Java Garbage Collector is an integral part of the Java Virtual Machine that automates memory management in Java programs. The Garbage Collector in Java is responsible for automatically reclaiming the memory occupied by objects that are no longer being used, freeing up resources and preventing memory leaks. By automatically detecting and removing unused objects, the garbage collector helps in optimizing memory usage and reducing the occurrence of "OutOfMemoryError" exceptions. With the deployment of Java as a portable, secure, and concurrent programming language, the mostly concurrent garbage collector has proved to be an excellent solution for Java's garbage collection task.

The use of this collector has been reported for the production JVMs of IBM, SUN, and BEA WebLogic JRockit, and has also been extensively investigated in academic research. The garbage collector in Java offers several advantages over explicit memory management, such as in languages like C. One advantage is that a garbage collector may incur less synchronization overhead compared to explicit memory management. This is because the garbage collector can deallocate multiple objects in the same garbage collection cycle, whereas explicit memory management requires synchronization for every free operation. Additionally, the garbage collection process has a significant impact on the overall runtime performance of a Java program. It is important to note that the efficiency of the garbage collection process can directly affect the performance of a Java program. Efficient memory management and garbage collection are therefore important goals in today's technology. One technique for optimizing Java's garbage collector is to tune it in order to reduce memory power consumption.

1. Serial Garbage Collector: This is the default garbage collector in Java for client applications. It is a simple, single-threaded garbage collector that pauses all application threads during garbage collection.
2. Parallel Garbage Collector: This garbage collector uses multiple threads to perform the garbage collection process, resulting in shorter pause times compared to the Serial Garbage Collector.
3. CMS Garbage Collector: This garbage collector aims to minimize the pause times experienced by application threads during garbage collection by performing most of the garbage collection work concurrently with application execution.
4. G1 Garbage Collector: The G1 garbage collector is designed to achieve both low pause times and high throughput by optimizing the garbage collection process based on application behavior and memory usage patterns.
5. Shenandoah Garbage Collector: This garbage collector focuses on reducing pause times by performing most of the garbage collection work concurrently with application execution, similar to the CMS Garbage Collector. Each garbage collector has its own strengths and weaknesses, and the choice of which one to use depends on the specific requirements of the application.

System.gc() and Runtime.gc()

It is worth mentioning that while Java provides automatic memory management through the garbage collector, there are also methods available to explicitly trigger garbage collection. However, it is generally not recommended to rely on explicit garbage collection calls using System.gc() or Runtime.gc(), as the garbage collector is designed to automatically handle memory management efficiently.

Difference between System.gc() and runtime.gc()