Mostly Asked Java Programming Interview Questions
Below, we are discussing some frequently asked Java Programming Interview Questions:
Q.1 How would you implement a Thread pool?
It is a generic implementation of a thread pool that takes the following input size of the pool to be constructed and the name of the class that implements runnable and constructs a thread pool with active threads that are waiting for activation.
Q.2 What are the benefits and drawbacks of reference counting In Garbage Collection?
An advantage of this scheme is that it will run in little chunks of time closely linked with the execution of the program. It is suitable for real-time environments where the program can’t be interrupted for a very long time
Q.3 Why we say Java as Pass-by-value?
When assigning an object to a variable, we are actually assigning the memory address of that object to the variable. So the value passed is really the memory location of the thing. This leads to object aliasing, which means you’ll have several variables referring to the same object on the heap.
Q.4 What are the access modifiers available In Java?
Access modifier specifies where a method or attribute often use.
The public is accessible from anyplace.
Protected is accessible from the same class and its subclasses.
Package/Default are accessible from the same package.
Private is only accessible from within the class.
Q.5 What’s the difference between a Switch Statement and an If Statement?
The switch statement is used to pick from multiple alternatives. The case values should be promoted to a to int value whereas If the statement is used to select from 2 alternatives. It uses a Boolean expression to decide that an alternative should be executed.
3. Java Programming Interview Questions for freshers
These are the some Java Programming Interview Questions for beginners:
Q.6 Explain synchronized methods and synchronized Statements?
Synchronized methods are methods that are declared with the keyword synchronized and in this, the thread executes a synchronized method only once it’s acquired the lock for the method’s object or class. Synchronized statements are similar to synchronized methods. It’s a block of code declared with synchronized keyword whereas a synchronized statement is often executed solely once a thread has acquired the lock for the object or class documented within the synchronized statement.
Q.7 What are the different ways that in which a thread will enter into waiting for the state?
There are 3 ways for a thread to enter into a waiting state. Also when you invoke its sleep() method, by interference on I/O, by unsuccessfully an attempt to acquire an object’s lock, or by invoking an object’s wait() method.
Q.8 What’s the difference between Static and Non Static variables?
A static variable associates with the class as a whole rather than with specific instances of a class. There’ll be only one value for the static variable for all instances of that category. Non-static variables take on unique values with each object instance.
Q.9 What’s the difference between notify and notifyall method?
Notify wakes up one thread that’s waiting for object’s monitor. In the case, if any threads are waiting on this object, one in every one of them is chosen to be awakened. The choice is arbitrary and occurs at the discretion of the implementation. notifyAll Wakes up all threads that are waiting on this object’s monitor. A thread waits on an object’s monitor by calling one of the wait ways.
Q.10 What are the different type of exceptions in Java?
There are 2 varieties of exceptions in java. Checked exceptions and uncurbed exceptions. Any exception that’s is derived from Throwable and Exception is termed checked exception except RuntimeException and its subclasses. The compiler can check whether or not the exception is caught or not at compile time. We want to catch the checked exception or declare within the throws clause. Any exception that’s derived from Error and Runtime Exception is termed unchecked exception. We ought not to explicitly catch an unchecked exception.
4. Java Programming Interview Questions for Experienced
These are the some Java Programming Interview Questions for professionals:
Q.11 Explain about the select method with an example?
Select part is useful in selecting text or part of the text.
Q.12 Will there be an abstract class with no abstract methods in it?
Yes.
Q.13 Can we outline private and protected modifiers for variables in interfaces?
No.
Q.14 What’s Garbage Collection? What’s the method that’s responsible for doing that in Java?
Reclaiming the unused memory by the invalid objects. The garbage collector is liable for this method.
Q.15 Will there be an abstract class with no abstract methods In It?
Yes.
Q.16 Will an interface has an Inner class?
Yes.
- public interface abc
- static int i=0;
- void dd();
- class a1 {
- a1() {
- int j;
- System.out.println(;
- public static void main(String a1[]) } }
Q.17 Explain user defined exception?
Other than the packages Java package libraries have already defined, the user will define his own exception classes by extending Exception class.
Q.18 What’s the difference between logical data independence and physical data independence?
Logical information Independence – Meaning immunity of external schemas to change in conceptual schema.
Physical information Independence – Meaning immunity of conceptual schema to changes within the internal schema.
5. Advanced Java Programming Interview Questions
Q.19 What are the practical benefits of importing a specific class instead of an entire Package?
It makes no difference in the generated class files since only the classes that literally use, reference by the generated class file. There’s another practical benefit to importing single classes, and this arises once 2 (or more) packages have classes with the same name. Take java.util.Timer and javax.swing.Timer, for example. If I import java.util.* and javax.swing.* and so try to use “Timer”, I get an error while compiling (the class name is ambiguous between each packages).
Let’s say what you really wished was the javax.swing.Timer class and the solely classes you plan on using in java.util are collection and HashMap. in this case, some people can prefer to import java.util.Collection and import java.util.HashMap rather than importing java.util.*. this can currently enable them to use Timer, Collection, HashMap, and different javax.swing classes while not using totally qualified class names in.
Q.20 State the number of methods that you implement if implement the Serializable Interface?
The Serializable interface is simply a “marker” interface, with no methods of its own to implement. different ’marker’ interfaces are
java.rmi.Remote
java.util.EventListener
Q.21 What does the “abstract” keyword mean in front of a method? A Class?
Abstract keyword declares either a way or a class. If a method has an abstract keyword before it, we call it an abstract method. An abstract method has nobody. It has only arguments and returns type. Abstract methods act as placeholder methods that implement within the subclasses.
Abstract classes can’t instantiate. If a class is said as abstract, no objects of that class creates. If a class contains any abstract method it should declare as abstract.
Q.22 When you’ll create A String Object As String Str = “abc”; Why can’t A Button Object Be Created As Button Bt = “abc”;? Justify.
You can’t create a button by Button bt= “abc”; is because “abc” is a literal string (something slightly different than a String object, by-the-way) and but may be a Button object. The only object in Java that may assign a literal String is java.lang.String. Important to note that you aren’t calling a java.lang.String constructor once you type String s = “abc”;
Q.23 Will Rmi and Corba based applications interact?
Yes, they’ll. RMI is available with IIOP as the transport protocol instead of JRMP.
Q.24 Describe Pass by reference and pass value?
Pass by value means all Java method arguments. However, Java will manipulate objects by reference, and all object variables themselves ar references.
Q.25 What’s a “stateless” Protocol?
Without getting into lengthy debates, it generally accepted that protocols like HTTP are stateless i.e. no retention of state between a transaction. That is a single request-response combination.
So, this was all in best Java Programming Interview Questions. Hope you like it.
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