Java Interview Questions (Part 1) | Read Now

Java Interview Questions are the list of all the basic asked questions in an interview when you apply for JAVA based job or internship.

These fundamental java interview questions are intended to familiarize both newcomers and experienced workers with the concepts, philosophies, and practices of Java.

1] How familiar with Java are you?

Java is a high-level programming language that was first developed in 1995 by Sun Microsystems. Java operates on a variety of platforms, including Windows, Mac OS, and several UNIX variations.

2] What platforms does the Java language support?

Java is available for Windows, Mac OS, and a variety of UNIX/Linux operating systems, including HP-Unix, Sun Solaris, Red Hat Linux, Ubuntu, CentOS, and others.

3] Is Java fully object-oriented language?

No, Java is not fully OOP language because it uses 8 primitive data types.

4] What are the unique characteristics of the Java computer language?

  • Simpler: Java is a straightforward language to learn. Because Java’s syntax is based on C++, it is easier to process in it.
  • Object-Oriented: Java follows the object-oriented model, which allows us to arrange our code and relate it to other objects.
  • Read-once, write-anywhere: Java implements the read-once, write-anywhere technique. A Java code can be run on any system. The Java source code (.java) is converted to bytecode (.class) that can be run on any operating system.
  • Independent from systems: Java is a user-friendly programming language that is independent of the operating system. It varies from certain computer languages, such as C and C++, which require the execution of a system. Java comes with a framework that it uses to write its code.
  • Powerful: Java is a powerful programming language because it uses strict data storage. Automated garbage collection, exception management, and other features make it more resilient.
  • Interpreted: Java supports the Just-in-Time (JIT) interpreter as well as the application execution compiler.
  • Neutral Architecture: Java is architecturally neutral because it is not based on a specific architectural style. The volume of data types in C can fluctuate depending on the layout (32 bit or 64 bit), which does not apply in Java.

5] How Stack differs from the Heap in Java computer language?

  • Memory storage: Stack’s memory is utilized by just one execution thread, whereas the heap’s memory is utilized by all the sectors of a defined application.
  • Life: Stack’s memory ends after the thread ‘s code implementation, whereas Heap’s memory ends after the whole implementation of an application ends.
  • Accessibility: The Stack’s memory is restricted on access, whereas the heap’s memory is accessible globally.
  • Use: Stack’s memory is utilized in storing up the local primitives, whereas heap’s memory stores an object when it is originally created.

6] Which variables do you refer to local, instance, and class?

  • Variables that are represented within methods, constructors, or blocks are referred to as local variables. The variable is defined and initialized within the method, and it will be eliminated once the operation is complete.
  • Instance variables are variables that exist both within and outside of a process. Those variables are executed when the class is activated.
  • Variables defined with the static keyword in a class that are not part of the methodology are referred to as class vars.

7] What is meant by default constructor? Can you present an illustration for the same?

The default constructor’s task is to implicitly assign any default values to the object. The code for the default constructor is:

class pen{  
int id;  
String name;  
  
void display(){System.out.println(id+" "+name);}  
  
public static void main(String args[]){  
pen s1=new pen();  
pen s2=new pen();  
s1.display();  
s2.display();  
}  
} 

8] Explain string pool in Java.

String pool in Java refers to the collection of various strings that are stored in Java’s heap memory. When any newer object is being initialized or created, Java will verify whether the same variable is stored or not in the heap’s pool. If it is being previously stored, then Java will return the same variable, otherwise, it will append the collection by creating a newer object and storing the string in the pool.

9] What various types of inheritance are used in Java?

  • Single-level
  • Multi-level
  • Hybrid
  • Hierarchical
  • Multiple

10] Can you make any constructor static?

The static methodology is purely related to some class and not to any object. So, as the constructors are called when an object is newly made, the constructors thus, cannot be made static. If anyone tries the same, an error in the compile-time will be displayed to the user.

11] Explain the central reason behind the restriction usage of pointers in Java.

Java does not support pointers as they are not secured and are very hard to comprehend.

12] What is meant my final variable in Java language?

The final variable refers to the variable that will be limited in terms of updating it. In simpler terms, you can not alter the value of that variable after its being declared as final.

13] How does overriding differ from the overloading methodology in Java?

  • Overloading refers to increase the code’s readability, whereas overriding permits a specific interpretation of some methodology that is initially present in the upper/super/parent classes.
  • Inheritance is compulsory in overriding, whereas in overloading it is not needed.
  • Return types in the overloading can be different, but in case of overriding, they should remain same.

14] Can you explain “this” in Java?

Yes, “this” is a keyword in Java that basically points out the present object. this has its own usage in Java with variables, constructors, methods, etc.

15] Which among the static and overload method can be overridden?

Among overload and static methodology, overload can be overridden as its the part of an object.

16] Why cannot the constructor be declared as final?

A constructor cannot be declared as final because it cannot be inherited. If in case, one tries to declare the constructor as final, the user will meet up a compilation error.

17] In Java, which class is known as the “superclass”?

The object class is the topmost/superclass.

18] Can you elaborate on the encapsulation concept?

Encapsulation in Java is the methodology to hide the attributes and their behaviors. It signifies the object’s independence from the other one.

19] Is it able to call one constructor inside the other one?

Yes, you can achieve that by utilizing the concept namely chaining of constructors that primarily uses the keyword “this”.

20] Define the tagging interface.

Marker or tagging interfaces are interfaces that do not contain any methods or constants.

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