Java Memory Management
Definition:
Memory management in Java refers to the process of allocating, managing, and reclaiming memory dynamically during the runtime of a program. Java uses automatic memory management via Garbage Collection (GC), which helps prevent memory leaks by automatically cleaning up memory that is no longer in use.
Key Concepts of Java Memory Management:
1. Heap Memory:
○ Definition: This is where all class instances (objects) and arrays are allocated. The heap is shared among all parts of an
application and divided into:
2. Stack Memory:
○ Definition: Stack memory is used for storing method calls and local variables. Each thread has its own stack, and memory is
automatically reclaimed when the method call completes.
3. Garbage Collection:
○ Definition: A mechanism that automatically reclaims memory by removing objects that are no longer reachable or in use.
Java Memory Structure:
- Method Area:
Stores class-level data such as static variables and method information. - Heap:
Stores instances of objects and arrays. - Stack:
Stores method calls and local variables. - PC Register (Program Counter Register):
Stores the address of the JVM instruction being executed. - Native Method Stack:
Used for native method execution (methods written in languages other than Java).
Example: Java Memory Management
public class MemoryExample {
public static void main(String[] args) {
// Stack memory allocation
int number = 100;
// Heap memory allocation
Person person = new Person(“Alice”, 25);
// Stack memory holds reference to the Person object in heap
person.displayInfo();
}
}
class Person {
String name;
int age;
// Constructor allocates memory in heap
public Person(String name, int age) {
this.name = name;
this.age = age;
}
public void displayInfo() {
// Accessing heap memory
System.out.println(“Name: ” + name + “, Age: ” + age);
}
}
Explanation:
● Stack Memory: The number variable and reference to the Person object are stored here.
● Heap Memory: The actual Person object (including name and age values) is stored in the heap.
Syntax:
Java automatically handles memory management, but you can influence memory handling using:
JVM Arguments:
You can configure memory settings using command-line options.
java -Xms512m -Xmx1024m MemoryExample
○ -Xms: Set the initial heap size.
○ -Xmx: Set the maximum heap size.
Manual Garbage Collection Request:
Though not recommended, you can manually suggest garbage collection.
System.gc();
Tasks:
1. Write a Java program that creates multiple objects. Simulate high memory usage and observe garbage collection by printing messages inside the object’s finalize() method.
2. Modify the example program above and add a static variable. Explain where it is stored in memory.
Course Video
YouTube Reference :
The training provides a basic overview of Java memory management, including concepts like heap and stack memory, garbage collection, and JVM memory configuration.
Yes, it includes examples demonstrating how objects are stored in heap memory and how stack memory is used for method execution.
Yes, exercises involve configuring JVM memory settings and observing the behavior of garbage collection in Java applications.
Yes, it’s designed for beginners with clear explanations and step-by-step examples.
Yes, it covers how to use JVM arguments like -Xms and -Xmx to set initial and maximum heap sizes.
Yes, the training is self-paced and accessible online anytime.
Yes, it explains how Java’s garbage collector works to automatically manage memory by reclaiming unused objects.
It typically takes a few hours to complete, depending on your learning pace.
Yes, this Java Memory Management training is completely free on Iqra Technology Academy’s website.
