Static variables in Java - Practice Problems & Coding Challenges

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Challenge - 5 Problems

💻 code output

intermediate

Output of static variable increment

What is the output of the following Java code?

Java

public class Test {
    static int count = 0;
    public Test() {
        count++;
    }
    public static void main(String[] args) {
        Test t1 = new Test();
        Test t2 = new Test();
        Test t3 = new Test();
        System.out.println(Test.count);
    }
}

A Compilation error

B 0

C 1

D 3

💻 code output

intermediate

Static variable behavior with multiple classes

What will be printed when running this Java code?

Java

class A {
    static int x = 5;
}
class B extends A {
    static int x = 10;
}
public class Main {
    public static void main(String[] args) {
        System.out.println(A.x);
        System.out.println(B.x);
    }
}

A 10\n10

B 5\n5

C 5\n10

D Compilation error

💻 code output

advanced

Static variable initialization order

What is the output of this Java code?

Java

public class Counter {
    static int count;
    static {
        count = count + 1;
    }
    public static void main(String[] args) {
        System.out.println(count);
    }
}

A 1

B Compilation error: variable count might not have been initialized

C Runtime error: NullPointerException

D 0

💻 code output

advanced

Static variable shared across threads

What is the output of this Java program?

Java

public class SharedCounter implements Runnable {
    static int counter = 0;
    public void run() {
        for(int i = 0; i < 1000; i++) {
            counter++;
        }
    }
    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(new SharedCounter());
        Thread t2 = new Thread(new SharedCounter());
        t1.start();
        t2.start();
        t1.join();
        t2.join();
        System.out.println(counter);
    }
}

A 2000

B Less than 2000

C 1000

D Compilation error

🧠 conceptual

expert

Static variable memory allocation

Which statement about static variables in Java is correct?

A Static variables are stored in the method area and shared among all instances.

B Static variables are stored in the stack and unique to each thread.

C Static variables are stored in the heap and shared among all instances of the class.

D Static variables are stored inside each object instance separately.