Static blocks in Java - Practice Problems & Coding Challenges

trophy

Challenge - 5 Problems

💻 code output

intermediate

Output of static block execution order

What is the output of this Java program that uses static blocks and a main method?

Java

public class Test {
    static {
        System.out.println("Static block 1");
    }
    public static void main(String[] args) {
        System.out.println("Main method");
    }
    static {
        System.out.println("Static block 2");
    }
}

A

Static block 1
Static block 2
Main method

B

Main method
Static block 1
Static block 2

C

Static block 2
Static block 1
Main method

D

Main method
Static block 2
Static block 1

💻 code output

intermediate

Static block and instance block output

What is the output when this Java program runs?

Java

public class Demo {
    static {
        System.out.println("Static block");
    }
    {
        System.out.println("Instance block");
    }
    public Demo() {
        System.out.println("Constructor");
    }
    public static void main(String[] args) {
        new Demo();
        new Demo();
    }
}

A

Instance block
Constructor
Instance block
Constructor
Static block

B

Static block
Instance block
Constructor
Instance block
Constructor

C

Static block
Constructor
Instance block
Constructor
Instance block

D

Instance block
Static block
Constructor
Instance block
Constructor

🔧 debug

advanced

Identify the error in static block usage

What error does this Java code produce?

Java

public class ErrorTest {
    static {
        int x = 10 / 0;
    }
    public static void main(String[] args) {
        System.out.println("Hello");
    }
}

A SyntaxError: division by zero not allowed

B NullPointerException at runtime

C No error, prints Hello

D ArithmeticException at runtime during class loading

🧠 conceptual

advanced

Static block and static variable initialization

Consider this Java class. What is the value of static variable 'count' after the class loads?

Java

public class Counter {
    static int count;
    static {
        count = 5;
    }
    static {
        count += 10;
    }
}

A 15

B 5

C 0

D Compilation error

💻 code output

expert

Static block with inheritance and output order

What is the output when running this Java program?

Java

class Parent {
    static {
        System.out.println("Parent static block");
    }
    {
        System.out.println("Parent instance block");
    }
    public Parent() {
        System.out.println("Parent constructor");
    }
}
class Child extends Parent {
    static {
        System.out.println("Child static block");
    }
    {
        System.out.println("Child instance block");
    }
    public Child() {
        System.out.println("Child constructor");
    }
}
public class TestInheritance {
    public static void main(String[] args) {
        new Child();
    }
}

A

Parent static block
Child static block
Child instance block
Child constructor
Parent instance block
Parent constructor

B

Child static block
Parent static block
Parent instance block
Parent constructor
Child instance block
Child constructor

C

Parent static block
Child static block
Parent instance block
Parent constructor
Child instance block
Child constructor

D

Parent instance block
Parent constructor
Child instance block
Child constructor
Parent static block
Child static block