Local Variables and Memory Management in Java Stack vs Heap

Keep It Local: Understanding Local Variables in Java ⚙️

Definitions

Local variables are variables declared inside a 

method, constructor, or block of code, accessible only within that scope. 

Once the method finishes, these variables are removed.

Local Variables and Memory Management in Java Stack vs Heap

Code Example

public class LocalExample {
    public static void main(String[] args) {
        int totalMarks = 0;  // Local variable declared inside the main method
        totalMarks = 90 + 85 + 78;
        System.out.println("The total marks are: " + totalMarks);  // Output: The total marks are: 253
    }
}
    

Methods and Memory Management in Java 🧠💾

Definitions

Stack Memory: Temporary storage for method calls and local variables.

Heap Memory: Long-term storage for objects created with new.

Examples

Stack Memory Example

public class MemoryExample {
    public static void main(String[] args) {
        int number = 5; // Local variable stored in the stack
        printNumber(number);
    }

    static void printNumber(int num) {
        System.out.println("The number is: " + num);
    }
}
    

Heap Memory Example

Local Variables and Memory Management in Java Stack vs Heap

public class HeapExample {
    public static void main(String[] args) {
        Student student = new Student(); // Object stored in the heap
        student.setName("Aarav");
        student.greet();
    }
}

class Student {
    String name;
    void setName(String name) {
        this.name = name;
    }
    void greet() {
        System.out.println("Hello, my name is " + name);
    }
}
    

Key Points

• Stack Memory: Stores local variables and method calls. Each method call creates a new stack frame, which is removed when the method completes.


• Heap Memory: Stores objects created with new and is managed by the Garbage Collector.

Parameters vs Arguments in Method Java