Basic and Advance Java Interview Questions And Answers

Download Java Interview Questions and Answers PDF

Elevate your Java interview readiness with our detailed compilation of 81 questions. These questions will test your expertise and readiness for any Java interview scenario. Ideal for candidates of all levels, this collection is a must-have for your study plan. Secure the free PDF to access all 81 questions and guarantee your preparation for your Java interview. This guide is crucial for enhancing your readiness and self-assurance.

81 Java Questions and Answers:

Java Job Interview Questions Table of Contents:

Java Job Interview Questions and Answers

1 :: What is a transient variable?

A transient variable is a variable that may not be serialized.

2 :: Which containers use a border layout as their default layout?

The window, Frame and Dialog classes use a border layout as their default layout in Java Programming.

3 :: How are Observer and Observable used in Java Programming?

Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.

4 :: What is synchronization and why is it important in Java Programming?

With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object’s value. This often causes dirty data and leads to significant errors.

5 :: What are synchronized methods and synchronized statements in Java Programming?

Synchronized methods are methods that are used to control access to an object. A thread only executes a synchronized method after it has acquired the lock for the method’s object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement.

6 :: What are three ways in which a thread can enter the waiting state in Java Programming?

A thread can enter the waiting state by invoking its sleep() method, by blocking on I/O, by unsuccessfully attempting to acquire an object’s lock, or by invoking an object’s wait() method. It can also enter the waiting state by invoking its (deprecated) suspend() method.

7 :: Can a lock be acquired on a class in Java Programming?

Yes, a lock can be acquired on a class. This lock is acquired on the class’s Class object.

8 :: What’s new with the stop(), suspend() and resume() methods in JDK 1.2?

The stop(), suspend() and resume() methods have been deprecated in JDK 1.2.

9 :: What is the preferred size of a component in Java Programming?

The preferred size of a component is the minimum component size that will allow the component to display normally.

10 :: What method is used to specify a container’s layout in Java Programming?

The setLayout() method is used to specify a container’s layout in Java Programming.

11 :: Which containers use a FlowLayout as their default layout in Java Programming?

The Panel and Applet classes use the FlowLayout as their default layout.

12 :: What state does a thread enter when it terminates its processing in Java Programming?

When a thread terminates its processing, it enters the dead state.

13 :: What is the Collections API in Java Programming?

The Collections API is a set of classes and interfaces that support operations on collections of objects.

14 :: What is the List interface in Java Programming?

The List interface provides support for ordered collections of objects.

15 :: How does Java handle integer overflows and underflows?

It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.

16 :: What is the Vector class in Java Programming?

The Vector class in Java Programming provides the capability to implement a growable array of objects

17 :: What modifiers may be used with an inner class that is a member of an outer class in Java Programming?

A (non-local) inner class may be declared as public, protected, private, static, final, or abstract.

18 :: If a method is declared as protected, where may the method be accessed in Java Programming?

A protected method may only be accessed by classes or interfaces of the same package or by subclasses of the class in which it is declared.

19 :: What is an Iterator interface in Java Programming?

The Iterator interface is used to step through the elements of a Collection.

20 :: How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8 characters in Java Programming?

Unicode requires 16 bits and ASCII require 7 bits. Although the ASCII character set uses only 7 bits, it is usually represented as 8 bits. UTF-8 represents characters using 8, 16, and 18 bit patterns. UTF-16 uses 16-bit and larger bit patterns.

21 :: What is the difference between yielding and sleeping in Java Programming?

When a task invokes its yield() method, it returns to the ready state. When a task invokes its sleep() method, it returns to the waiting state.

22 :: Is sizeof a keyword in Java Programming?

The sizeof operator is not a keyword in Java Programming.

23 :: What are wrapped classes in Java Programming?

Wrapped classes are classes that allow primitive types to be accessed as objects.

24 :: Does garbage collection guarantee that a program will not run out of memory?

No, it doesn’t. It is possible for programs to use up memory resources faster than they are garbage collected. It is also possible for programs to create objects that are not subject to garbage collection

25 :: What is the difference between preemptive scheduling and time slicing in Java Programming?

Under preemptive scheduling, the highest priority task executes until it enters the waiting or dead states or a higher priority task comes into existence. Under time slicing, a task executes for a predefined slice of time and then reenters the pool of ready tasks. The scheduler then determines which task should execute next, based on priority and other factors.