Java Interview Questions for Junior Developers — Part 4

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Welcome to the fourth installment of our series on core Java interview questions for junior developers. In this article, we will delve into a new set of topics that are commonly assessed during Java interviews.

Java Interview Questions for Junior Developers — Part 1

Java Interview Questions for Junior Developers — Part 2

Java Interview Questions for Junior Developers — Part 3

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What is the purpose of the Comparable interface in Java? Give an example.

• The Comparable interface is used to define the natural ordering of objects.

public class Person implements Comparable<Person> {
    private String name;

    // Constructor and other methods

    @Override
    publicint compareTo(Person otherPerson) {
        return this.name.compareTo(otherPerson.name);
    }
}

Explain the purpose of the Object class in Java.

• The Object class is the root class of all classes in Java.
• It provides methods that are inherited by all other classes, such as equals(), hashCode(), toString(), and getClass().

What is the difference between an instance variable and a local variable in Java?

• An instance variable is declared inside a class but outside any method, constructor, or block. It is associated with instances of the class.
• A local variable is declared within a method, constructor, or block and is only accessible within that scope.

Explain the difference between a shallow copy and a deep copy in Java.

• A shallow copy creates a new object that shares the same references to the objects as the original. Changes to the referenced objects are reflected in both.
• A deep copy creates a new object and recursively copies all referenced objects, creating new instances. Changes to the referenced objects do not affect each other.

What is the purpose of the synchronized keyword in Java? Give an example.

• The synchronized keyword is used to provide thread-safety by allowing only one thread at a time to execute a synchronized block or method.

public synchronized void incrementCounter() {
    // Thread-safe code here
}

Ensuring Thread Safety and Concurrent Access

Explain the purpose of the static import statement in Java. Give an example.

• The static import statement is used to import static members of a class directly into another class, without specifying the class name.

import static java.lang.Math.PI;
import static java.lang.Math.sqrt;

public class Circle {
    public double calculateArea(double radius) {
        return PI * sqrt(radius);
    }
}

What is the purpose of the try-with-resources statement in Java? Give an example.

• The try-with-resources statement is used to automatically close resources that implement the AutoCloseable interface.

try (BufferedReader br = new BufferedReader(new FileReader("file.txt"))) {
    // Read from the file
} catch (IOException e) {
    // Exception handling
}

What is the purpose of the System.arraycopy() method in Java? Give an example.

• The System.arraycopy() method is used to efficiently copy elements from one array to another.

int[] sourceArray = {1, 2, 3};
int[] destinationArray = new int[3];
System.arraycopy(sourceArray, 0, destinationArray, 0, sourceArray.length);

What is the purpose of the StringTokenizer class in Java? Give an example.

• The StringTokenizer class is used to tokenize (split) a string into tokens based on a delimiter.

String str = "Hello, World!";
StringTokenizer tokenizer = new StringTokenizer(str, ",");
while (tokenizer.hasMoreTokens()) {
    System.out.println(tokenizer.nextToken());
}

Explain the instanceof operator in Java. Give an example.

• The instanceof operator is used to check if an object is an instance of a particular class or its subclass.

Animal animal = new Dog();
if (animal instanceof Dog) {
    // Do something specific for dogs
}

Now that you have a solid foundation in these areas, continue practicing with coding examples and exploring real-world scenarios to strengthen your skills. Additionally, stay updated with the latest advancements and best practices in Java development, as the field is constantly evolving.

In the next article, we will continue our journey through core Java interview questions, focusing on the basics of Java. But it will be the last article about the basics. Incoming articles will mostly focus on more detailed topics such as exception handling, multithreading, generics, Java I/O etc. So, stay tuned and keep up the enthusiasm as we delve deeper into the Java ecosystem!

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