Basic Java Questions For Freshers
Common Questions for Freshers in a Java Interview
Basic Java questions for freshers are the fundamental interview questions based on the Java programming language. These questions aim to evaluate the candidates' basic understanding and knowledge of Java concepts, such as object-oriented programming, data types, control structures, inheritance, and encapsulation. They also assess the familiarity of candidates with Java programming tools and their ability to write basic Java code. These questions serve as a starting point to gauge a candidate's technical proficiency and aptitude for software development, making them a crucial part of any Java fresher's interview preparation.
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1 - What is Java?
Java is a high-level object-oriented programming language. It was developed by Sun Microsystems in 1995. It is known for its simplicity, reliability, and platform-independence, meaning that Java programs can run on any platform that has a Java Virtual Machine (JVM).
2) What is the difference between JDK and JRE?
JDK stands for Java Development Kit, and it is a software development environment used for writing and compiling code. It includes a Java compiler, Java Runtime Environment (JRE), and other tools. On the other hand, JRE stands for Java Runtime Environment, which is an environment that includes only the tools needed to run Java programs, but not to develop them.
3) What is an object in Java?
An object is a key concept in Java and is used to represent real-world entities. It encapsulates both data and code, and it is an instance of a class. Objects interact with each other by calling methods and exchanging data, making Java a truly object-oriented language.
4) What is the difference between heap and stack memory in Java?
In Java, objects are allocated memory from the heap, which is a larger memory space shared by all threads of a program. This space is managed by the JVM and is used for dynamic memory allocation. On the other hand, stack memory is used for the execution of methods and stores local variables and method parameters. It is smaller in size and is used for short-lived objects.
5) What is a constructor in Java?
A constructor is a special method used for initializing objects. It has the same name as the class and is called automatically when an object of that class is created. It is used to set initial values for the object's member variables and can be overloaded for different types of initialization.
6) What is the difference between an abstract class and an interface?
An abstract class contains abstract methods that must be implemented by its subclasses, while an interface contains only method signatures and constant declarations. A class can implement multiple interfaces, but it can only extend one abstract class.
7) What is a wrapper class in Java?
Wrapper classes in Java provide a way to convert primitive data types (int, boolean, etc.) into objects. They are used to represent primitive data types when working with collections, as they can only store objects, not primitive types.
8) What is the ‘this’ keyword in Java?
The ‘this’ keyword refers to the current object within a class. It can be used to access the current object's methods, constructors, and member variables. It is commonly used in constructors and setter methods to differentiate class variables from local variables with the same name.
9) What is the difference between a static method and an instance method?
Static methods belong to a class and can be called without an instance of the class, while instance methods can only be called on an object of the class. Static methods are commonly used as utility methods, while instance methods are used for manipulating individual objects.
10) What is the difference between a method overloading and method overriding?
Method overloading is when a class has multiple methods with the same name but different parameters. Method overriding is when a subclass has a method with the same name and parameters as its superclass, allowing it to provide its own implementation. Method overloading is resolved at compile time, while method overriding is resolved at runtime.
11) What is a package in Java?
A package in Java is a way of organizing classes and interfaces into different folders, making it easier to manage and reuse code. Packages also provide a way to control access to classes by using package-level access modifiers.
12) What is the default value of a boolean variable in Java?
The default value of a boolean variable in Java is ‘false’. It can only be set to ‘true’ or ‘false’ and is commonly used for storing true/false conditions in control structures.
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13) What is polymorphism in Java?
Polymorphism is a key principle of object-oriented programming where objects can take on different forms or have multiple behaviors. In Java, this can be achieved through method overriding and method overloading.
14) What is a try-catch block in Java?
A try-catch block is used to handle exceptions in Java. The ‘try’ block contains code that may throw an exception, while the ‘catch’ block is used to catch and handle the exception. It prevents the program from crashing and allows for graceful error handling.
15) What is the difference between == and .equals() in Java?
‘==’ is a comparison operator and is used to compare primitive data types for equality, while .equals() is a method used to compare objects. It compares the content of the objects, not the memory location. For example, ‘str1.equals(str2)’ would return true if the content of both strings is the same, even if they are stored in different memory locations.
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