Static Block vs Instance Initialization Block in Java (With Example)

 

In Java, understanding the order of execution between static blocks and instance initialization blocks is essential for managing class-level and object-level setup.

• Static Block (static { ... }): Belongs to the class itself, not to any specific object. It executes exactly once when the class is loaded into memory by the JVM, well before any instances are constructed.

• Instance Initialization Block ({ ... }): Belongs to individual object instances. It executes every time a new object is created, running immediately before the constructor body.

 Code Example - InitBlockStaticBlock.java

 public class InitBlockStaticBlock {

    // 1. Static Initialization Block: Runs once when the class is loaded
    static {
        System.out.println("Executing static block (Class loaded)");
    }

    // 2. Instance Initialization Block: Runs once per object instantiation
    {
        System.out.println("Executing instance init block (Object created)");
    }

    public static void main(String[] args) {
        System.out.println("--- Inside main method ---");

        InitBlockStaticBlock obj1 = new InitBlockStaticBlock();
        InitBlockStaticBlock obj2 = new InitBlockStaticBlock();
        InitBlockStaticBlock obj3 = new InitBlockStaticBlock();
    }
}

 

Output :- 

Executing static block (Class loaded)
--- Inside main method ---
Executing instance init block (Object created)
Executing instance init block (Object created)
Executing instance init block (Object created)