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Java is a general-purpose programming language and if in case you come up with a situation where there are unused data in your program and you do not know how to handle it, Garbage Collection in Java comes in handy. So, I’m writing this article to help you out with handling these functions.
I’ll be covering the topics in the following order:
Let’s get started!
In Java, programmers face the issue of having to destroy the objects that are out of use. But with the Garbage Collector, this can be easily taken care of. The main objective of this Garbage Collector is to free heap memory by destroying the objects doesn’t contain a reference. The technique is known as Garbage Collection.
It is also considered as a program that helps to perform automatic memory management. When Java programs are run on the JVM, objects are created on the heap, which is actually a portion of memory that is dedicated to the program. Eventually, some objects will no longer be needed. The garbage collector finds these unused objects and deletes them to free up some memory.
Now, let’s understand how this automatic garbage collection works in Java.
Note: An object is said to be eligible for garbage collection iff it is unreachable.
Garbage Collection is a process of working with the Heap memory and also mark or identify the unreachable objects and destroy them with compaction.
Garbage collection in Java is an automatic process and the programmer does not have to explicitly mark objects to be deleted. The implementation mainly lives in the JVM. Each JVM can implement garbage collection. The only requirement is that it should meet the JVM specification.
Even though there are many JVMs available, Oracle’s HotSpot is by far the most common as it offers a robust and mature set of garbage collection options.
All of HotSpot’s garbage collectors implement a generational collection strategy that categorizes objects by age. The rationale behind generational garbage collection is that most objects are short-lived and will be ready for garbage collection soon after creation.
Now let’s see what are the different types of garbage collectors.
The JVM provides four different garbage collectors, all of them generational. Each one has its own advantages and limitations. The choice of which garbage collector to use lies with the user and there can be numerous differences in the throughput and application pauses.
There are namely 4 types of garbage collectors.
Let’s understand the advantages of Garbage collection in Java.
The best approach to adapt to Java garbage collection is by setting flags on the JVM. Flags have the ability to adjust the garbage collector to be used. It helps in making it the best suited for backend processing where long pauses for garbage collection are acceptable.
Another thing to note here is, the CMS garbage collector is designed to minimize pauses which makes it ideal for GUI applications where responsiveness is highly important. Additional fine-tuning can be accomplished by changing the size of the heap or its sections and measuring garbage collection efficiency.
Let’s take a look at this program.
class Edureka { int a; int b; public void setData(int c,int d) { a=c; b=d; } public void showData() { System.out.println("Value of a = "+a); System.out.println("Value of b = "+b); } public static void main(String args[]) { Edureka e1 = new Edureka(); Edureka e2 = new Edureka(); e1.setData(1,2); e2.setData(3,4); e1.showData(); e2.showData(); //Edureka e3; //e3=e2; //e3.showData(); //e2=null; //e3.showData(); //e3=null; //e3.showData(); } }
In this case, the two objects and two reference variables are created. If you add another command e3=Null, two reference variables will point to the same object. And if there is no reference to the variable, e3=e2;e3.showData();At this point, there are no references pointing to the object and it becomes eligible for garbage collection.
This brings us to the end of this ‘Garbage Collection in Java’ article. We have learned how to remove unused objects in the heap and the different types of collection.
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