Java Interview Preparation || 100+ Quality Questions Covered

Explain how the Java virtual machine runs bytecode, how the JRE bundles the JVM and libraries to run programs, and how the JDK adds development tools like the compiler.

Explain the difference between path and classpath, two environment variables that locate binary executables and class files, and show how the compiler uses classpath to resolve imports by package name.

Java is platform independent because compiled class files become bytecode executed by the JVM. The JVM adapts to each platform, enabling run anywhere with magical bytecode.

Compare Java and C++ by highlighting platform dependence, byte code, pointers, structures and unions, multiple inheritance, operator overloading, and call by value versus call by reference.

Master the four OOP concepts in Java. Explore polymorphism, inheritance, abstraction, and encapsulation through real-life examples: a mobile phone, a parent-child relation, a car driver, and encapsulation with getters/setters.

Learn how to prevent inheritance and method overriding in Java using the final keyword, with Eclipse examples showing final class and final methods.

Discover that declaring the main method as final in a parent class prevents child classes from overriding it, causing compiler errors and illustrating the consequences.

Java does not support multiple inheritance with classes due to the diamond problem. A class can implement multiple interfaces, avoiding ambiguity.

Learn the execution order of static block, block, constructor, and test method in Java, with static block executing before main.

Discover how to run a public static void main inside an abstract class in Java. Understand that abstract classes can include concrete methods and still be executed.

Understand marker interfaces in Java; they contain no fields or methods and serve to convey information to the compiler or JVM, with examples like Serializable and Cloneable.

Explore the difference between checked and unchecked exceptions in Java, showing compile time file not found errors and runtime division by zero, with try catch and throws usage.

Learn how to create a custom exception in Java by extending the exception class, using a constructor that passes a message to super, and throwing it in file operations.

Discover how the finally block runs after try or catch, even with exceptions, except when the application exits via System.exit.

Explore the difference between list and set in Java. Lists allow duplicates and preserve insertion order, while sets enforce unique values.

Discover how to make Java collections read-only by using unmodifiable collections for lists and sets, preventing any add or remove operations.

Explore how the Java unsupported operation exception works, and see how unmodifiable lists and read-only collections throw when you try to add or remove elements in Eclipse.

Explain how peek, poll, and remove differ: peek returns the head without removal (null if empty); poll and remove remove the head (remove throws No such element exception if empty).

Demonstrate how to implement a singleton class in Java by using a private constructor, a private static instance, and a public static getInstance method to guarantee a single object.

Use the factory design pattern in Java to decide at runtime whether to instantiate a laptop or a desktop through a computer factory, which returns a computer interface implementation.

Learn how to create an immutable class in Java by making the class final, private fields, and exposing only getters through a constructor, copying nested objects when needed.

Explore Java 8 features like functional interfaces, stream, optional, string joiner, and the date-time API, and learn to set up Eclipse with Java 8 support.

Explore how a functional interface in Java 8 is defined by a single abstract method and marked with @FunctionalInterface, while supporting default and static methods.

Showcases how a lambda expression creates an instance of a functional interface in Java 8, implementing the single abstract method get square to compute a value's square.

Learn how the Stream API handles large collections by filtering, mapping, and collecting data in one line. See examples filtering by id, mapping to ideas, and collecting to lists.

Learn what Optional is in Java 8 and how it helps prevent null pointer exceptions by wrapping potentially null values, checking presence with isPresent(), and using examples with arrays.

Learn how to use string joiner in java 8 with delimiter, prefix, and suffix to join names and countries, including parallel streams, through hands-on eclipse examples.

Learn how Java serialization converts an object's state into a byte stream for storage in database, filesystem, or memory, using the Serializable marker interface and object output streams.

Learn how deserialization converts a byte stream back into a Java object, the reverse of serialization, by reading a saved Person with object input stream.

Learn how transient variables in Java are not serialized, triggering default values on deserialization, and how to mark fields with the transient keyword to save storage.

SerialVersionUID is a private static final long used in serialization to verify compatibility between sender and receiver; increment it when you change a serialized class to avoid InvalidClassException.

Discover five ways to create a Java object: using the new keyword, reflection with Class.newInstance, constructor-based reflection via newInstance, deserialization, and cloning, noting that deserialization and cloning bypass constructors.

Explore the ternary operator in Java as a compact conditional using a boolean condition with ? and : to select 'greater than zero' or 'less than zero'.

Celebrate completing the Java interview preparation course and master the 100+ quality questions that help you crack your next Java interview; invite additional questions to strengthen this course.