Object Oriented Programming

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Questions and Answers

Explain the difference between `==` and the `.equals()` method when comparing objects in Java. Why is it important to use `.equals()` for comparing the content of objects?

== compares references, checking if two variables point to the same object in memory. .equals() compares the actual content of the objects. Using .equals() ensures you're comparing values, not memory locations.

Describe the concept of method overloading in Java. Give an example of how method overloading can be useful in a class.

Method overloading is when a class has multiple methods with the same name but different parameters (different types, number, or order). This allows you to use the same method name for similar operations on different data types or with varying inputs, enhancing code readability and flexibility. For example, several add methods that can take in different numbers of parameters.

Explain the purpose of `static` variables and methods in Java. How do they differ from instance variables and methods?

static variables and methods belong to the class itself, not to any specific instance of the class. Instance variables and methods belong to each object. static members are shared among all instances, while instance members are unique to each instance.

What is the difference between an `interface` and an `abstract class` in Java? When would you choose to use one over the other?

An <code>interface</code> provides complete abstraction; it only declares methods (no implementation). An <code>abstract class</code> can have both abstract and concrete methods. Use an <code>interface</code> when unrelated classes need to implement common methods. Use an <code>abstract class</code> when there is a class hierarchy and some common implementation is needed. Signup and view all the answers

Explain the concept of exception handling in Java. Why is it important, and what are the key keywords used in exception handling?

Exception handling is a mechanism to handle runtime errors without program termination. It's important for robust code. The keywords are: <code>try</code> (encloses code that might throw an exception), <code>catch</code> (handles a specific type of exception), <code>finally</code> (always executes, even if an exception is thrown), and <code>throw</code> (used to explicitly throw an exception). Signup and view all the answers

Describe the difference between checked and unchecked exceptions in Java. Give an example of each.

Checked exceptions are checked at compile time; the compiler forces you to handle them (e.g., <code>IOException</code>). Unchecked exceptions occur at runtime and are not checked at compile time (e.g., <code>NullPointerException</code>). Signup and view all the answers

What is multithreading in Java, and why is it useful? Explain how you can create a new thread in Java using the `Runnable` interface.

Multithreading is the ability of a program to execute multiple threads concurrently, improving performance. To create a thread using <code>Runnable</code>, you implement the <code>Runnable</code> interface, define the <code>run()</code> method (the thread's execution logic), create a <code>Thread</code> object passing your <code>Runnable</code> instance, and then call <code>start()</code> on the <code>Thread</code> object. Signup and view all the answers

What are the different states in the lifecycle of a thread in Java? Briefly describe each state.

The states are: New (thread created but not started), Runnable (ready to run), Running (currently executing), Blocked/Waiting (temporarily inactive, waiting for a resource or event), and Terminated (execution completed). Signup and view all the answers

Explain the purpose of the `synchronized` keyword in Java. How does it help prevent race conditions in multithreaded environments?

The <code>synchronized</code> keyword is used to control access to shared resources by multiple threads. It ensures that only one thread can execute a synchronized method or block of code at a time, preventing race conditions by providing mutual exclusion. Signup and view all the answers

Describe the purpose and function of the `Executor` framework in Java concurrency. How does it simplify the management of threads compared to explicitly creating and managing `Thread` objects?

The <code>Executor</code> framework provides a higher-level abstraction for managing thread pools. It simplifies thread management by handling thread creation, scheduling, and execution, allowing developers to focus on the tasks to be performed rather than the low-level details of thread management. <code>Executor</code> hides the complexity of managing threads and promotes efficient use of resources. Signup and view all the answers

Flashcards

Programming Style (Java)

A set of rules that define how Java code should be written and formatted for readability and consistency.

Data Types in Java

Numeric (int, double), text (String), true/false (boolean), and single characters (char). Defines what type of data a variable can hold.