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Top 100 TCS Interview Questions and Answers

Top 100 TCS Interview Questions and Answers

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1. What is the fundamental difference between a class and an object in object-oriented programming?

Answer:
A class is a blueprint or template that defines the structure and behavior of an object. It encapsulates data for the object and provides methods to operate on that data. An object, on the other hand, is an instance of a class. It represents a real-world entity and has a unique state and behavior.


2. Can you explain the concept of inheritance in object-oriented programming?

Answer:
Inheritance is a fundamental concept in object-oriented programming that allows a class (subclass) to inherit properties and behaviors from another class (superclass). The subclass can access the members (fields and methods) of the superclass and also add its own unique members. This promotes code reuse and helps create a hierarchical relationship between classes.


3. What is the significance of polymorphism in object-oriented programming and how is it achieved in Java?

Answer:
Polymorphism allows an object to take on different forms or have multiple behaviors. In Java, polymorphism is achieved through method overloading and method overriding. Method overloading involves having multiple methods in the same class with the same name but different parameter lists. Method overriding occurs when a subclass provides a specific implementation for a method defined in its superclass.


4. What is the difference between ArrayList and LinkedList in Java?

Answer:

  • ArrayList:
  • Implemented as a dynamic array.
  • Provides fast random access to elements.
  • Slower for inserting or deleting elements in the middle.
  • Good for scenarios with more reads and less modification.
  • LinkedList:
  • Implemented as a doubly linked list.
  • Efficient for insertions and deletions in the middle.
  • Slower for random access.
  • Suitable for scenarios with frequent insertions and deletions.

5. How does garbage collection work in Java?

Answer:

Java’s garbage collector automatically manages memory by reclaiming objects that are no longer in use. It periodically looks at all objects in the memory and identifies those without references (unreachable objects). These objects are then marked for garbage collection.


6. Explain the concept of polymorphism in Java.

Answer:

Polymorphism refers to the ability of a class to take on multiple forms. In Java, it can be achieved through method overloading and method overriding. Method overloading allows a class to have multiple methods with the same name but different parameters. Method overriding occurs when a subclass provides a specific implementation for a method defined in its superclass.


7. What is the purpose of the static keyword in Java?

Answer:

  • static is used to create variables and methods that belong to the class rather than to any specific instance.
  • static variables are shared among all instances of a class.
  • static methods can be called without an instance of the class.

8. Explain the concept of abstraction in Java.

Answer:

Abstraction is the process of hiding the implementation details and exposing only the relevant features of an object. In Java, this is achieved through abstract classes and interfaces. Abstract classes cannot be instantiated and may have abstract methods that must be implemented by subclasses. Interfaces define a contract for methods without providing an implementation.


9. What is the purpose of the final keyword in Java?

Answer:

  • When applied to a variable, it makes the variable a constant and its value cannot be changed.
  • When applied to a method, it prevents the method from being overridden by subclasses.
  • When applied to a class, it prevents the class from being subclassed.

10. Explain the concept of exception handling in Java.

Answer:

Exception handling is a mechanism to deal with runtime errors in a program. It involves catching exceptions that occur during program execution and taking appropriate actions. This is done using try, catch, finally, and throw keywords. The try block contains the code that might throw an exception, and the catch block handles the exception.


11. What are Java annotations and how are they used?

Answer:

Annotations provide metadata about the program, which can be used by the compiler or other tools. They start with @ symbol and are placed above classes, methods, variables, etc. Annotations are widely used for tasks like code generation, documentation, and runtime behavior.


12. Explain the concept of multithreading in Java.

Answer:

Multithreading allows a program to execute multiple threads concurrently. Each thread represents a separate flow of control within a program. This enables the program to perform multiple tasks at the same time, improving efficiency. Java provides built-in support for multithreading through the Thread class and the Runnable interface.


13. What is the difference between HashMap and HashTable in Java?

Answer:

  • HashMap is not synchronized and is not thread-safe. It performs better in non-threaded environments.
  • HashTable is synchronized and is thread-safe, but it is slower due to synchronization overhead.
  • HashMap allows null values and one null key, whereas HashTable does not allow null keys or values.
  • HashMap is preferred for most use cases due to its better performance.

14. What is the purpose of the super keyword in Java?

Answer:

The super keyword is used to refer to the immediate parent class’s instance variable or method. It is used to distinguish between the members of a subclass and the members of the superclass with the same name. It is also used to invoke the superclass’s constructor.


15. Explain the concept of Inheritance in Java.

Answer:

Inheritance is a fundamental concept in object-oriented programming where a class (subclass) inherits the properties and behaviors of another class (superclass). It allows the subclass to reuse code and extend the functionality of the superclass. This facilitates code reusability and helps in creating a hierarchical structure of classes.


16. What is the purpose of the this keyword in Java?

Answer:

The this keyword refers to the current instance of a class. It is used to differentiate between instance variables and parameters with the same name. It can also be used to invoke constructors from other constructors in the same class.


17. Explain the concept of encapsulation in Java.

Answer:

Encapsulation is a fundamental concept in object-oriented programming that involves bundling data (attributes) and methods (functions) that operate on the data within a single unit, called a class. It restricts access to some of the object’s components, typically the internal data, from the outside. This protects the integrity of the data and ensures that it is accessed and modified only through well-defined methods.


18. What is a constructor in Java?

Answer:

A constructor is a special method in a Java class that is used to initialize an object. It has the same name as the class and does not have a return type. Constructors are automatically called when an object is created using the new keyword. They are used to set initial values for object attributes and perform other setup tasks.


19. Explain the concept of interfaces in Java.

Answer:

An interface in Java is a reference type that is similar to a class. It is a collection of abstract methods and constant declarations. An interface provides a contract for what a class can do, without specifying how it does it. Classes implement interfaces by providing concrete implementations for all the methods defined in the interface.


20. What is the purpose of the equals method in Java?

Answer:

The equals method in Java is used to compare the content of two objects for equality. By default, it compares object references, but it can be overridden in a class to provide custom comparison logic. This allows objects of a class to define their own notion of equality.


21. Explain the concept of composition in Java.

Answer:

Composition is a design technique in object-oriented programming where a class contains an instance of another class as a member. This allows for building complex relationships between objects. It is often used to represent a “has-a” relationship, where one object has another as part of its state.


22. What is the purpose of the toString method in Java?

Answer:

The toString method is used to obtain a string representation of an object. It is automatically called when an object is concatenated with a string using the + operator or when println is called to print an object. By overriding this method, a class can provide a meaningful string representation of its objects.


23. Explain the concept of packages in Java.

Answer:

Packages in Java are used to organize classes and interfaces into groups. They help prevent naming conflicts and provide a way to control access to class members. A package is a directory that contains a group of related classes and interfaces. It also allows for better modularization and reusability of code.


24. What is the purpose of the static block in Java?

Answer:

The static block in Java is a block of code that is executed when the class is first loaded into memory by the Java Virtual Machine (JVM). It is used to perform one-time initialization tasks for the class, such as setting up static variables or initializing static resources.


25. Explain the concept of method overriding in Java.

Answer:

Method overriding occurs when a subclass provides a specific implementation for a method that is already defined in its superclass. It allows a subclass to provide a specialized implementation of a method, while still maintaining the same method signature. This enables polymorphic behavior, where a method call is resolved at runtime based on the actual object type.


26. What is the purpose of the instanceof operator in Java?

Answer:

The instanceof operator in Java is used to test whether an object is an instance of a particular class or interface. It returns true if the object is an instance of the specified type, or one of its subclasses or subinterfaces. It is often used to perform type checking before type casting.


27. Explain the concept of abstract classes in Java.

Answer:

An abstract class in Java is a class that cannot be instantiated on its own. It serves as a blueprint for other classes that extend it. It may contain abstract methods, which are declared but not implemented in the abstract class. Subclasses must provide concrete implementations for these abstract methods.


28. What is the purpose of the final variable in Java?

Answer:

A final variable in Java is a constant whose value cannot be changed after it is initialized. It must be assigned a value exactly once, either at the time of declaration or in the constructor. Attempting to reassign a final variable will result in a compilation error.


29. Explain the concept of anonymous classes in Java.

Answer:

An anonymous class in Java is a class without a name. It is typically used for one-time use when creating an instance of a class and providing its implementation at the same time. Anonymous classes are declared and instantiated in a single expression and are often used for event handling and callback functions.


30. What is the purpose of the try-catch block in Java?

Answer:

The try-catch block in Java is used for exception handling. The code within the try block is monitored for exceptions. If an exception occurs, it is caught by the `catch` block, which contains the code to handle the exception. This prevents the program from terminating abruptly due to an unhandled exception.


31. Explain the concept of method overloading in Java.

Answer:

Method overloading in Java allows a class to have multiple methods with the same name but different parameter lists. This enables a class to provide different versions of a method for different types or numbers of arguments. It improves code readability and maintainability.


32. What is the purpose of encapsulation in Java?

Answer:

Encapsulation is a fundamental concept in object-oriented programming that involves bundling data (attributes) and methods (functions) that operate on the data within a single unit, called a class. It restricts access to some of the object’s components, typically the internal data, from the outside. This protects the integrity of the data and ensures that it is accessed and modified only through well-defined methods.


33. What is a constructor in Java?

Answer:

A constructor is a special method in a Java class that is used to initialize an object. It has the same name as the class and does not have a return type. Constructors are automatically called when an object is created using the new keyword. They are used to set initial values for object attributes and perform other setup tasks.


34. Explain the concept of interfaces in Java.

Answer:

An interface in Java is a reference type that is similar to a class. It is a collection of abstract methods and constant declarations. An interface provides a contract for what a class can do, without specifying how it does it. Classes implement interfaces by providing concrete implementations for all the methods defined in the interface.


35. What is the purpose of the equals method in Java?

Answer:

The equals method in Java is used to compare the content of two objects for equality. By default, it compares object references, but it can be overridden in a class to provide custom comparison logic. This allows objects of a class to define their own notion of equality.


36. Explain the concept of composition in Java.

Answer:

Composition is a design technique in object-oriented programming where a class contains an instance of another class as a member. This allows for building complex relationships between objects. It is often used to represent a “has-a” relationship, where one object has another as part of its state.


37. What is the purpose of the toString method in Java?

Answer:

The toString method is used to obtain a string representation of an object. It is automatically called when an object is concatenated with a string using the + operator or when println is called to print an object. By overriding this method, a class can provide a meaningful string representation of its objects.


38. Explain the concept of packages in Java.

Answer:

Packages in Java are used to organize classes and interfaces into groups. They help prevent naming conflicts and provide a way to control access to class members. A package is a directory that contains a group of related classes and interfaces. It also allows for better modularization and reusability of code.


39. What is the purpose of the static block in Java?

Answer:

The static block in Java is a block of code that is executed when the class is first loaded into memory by the Java Virtual Machine (JVM). It is used to perform one-time initialization tasks for the class, such as setting up static variables or initializing static resources.


40. Explain the concept of method overriding in Java.

Answer:

Method overriding occurs when a subclass provides a specific implementation for a method that is already defined in its superclass. It allows a subclass to provide a specialized implementation of a method, while still maintaining the same method signature. This enables polymorphic behavior, where a method call is resolved at runtime based on the actual object type.


41. What is the purpose of the instanceof operator in Java?

Answer:

The instanceof operator in Java is used to test whether an object is an instance of a particular class or interface. It returns true if the object is an instance of the specified type, or one of its subclasses or subinterfaces. It is often used to perform type checking before type casting.


42. Explain the concept of abstract classes in Java.

Answer:

An abstract class in Java is a class that cannot be instantiated on its own. It serves as a blueprint for other classes that extend it. It may contain abstract methods, which are declared but not implemented in the abstract class. Subclasses must provide concrete implementations for these abstract methods.


43. What is the purpose of the final variable in Java?

Answer:

A final variable in Java is a constant whose value cannot be changed after it is initialized. It must be assigned a value exactly once, either at the time of declaration or in the constructor. Attempting to reassign a final variable will result in a compilation error.


44. Explain the concept of anonymous classes in Java.

Answer:

An anonymous class in Java is a class without a name. It is typically used for one-time use when creating an instance of a class and providing its implementation at the same time. Anonymous classes are declared and instantiated in a single expression and are often used for event handling and callback functions.


45. What is the purpose of the try-catch block in Java?

Answer:

The try-catch block in Java is used for exception handling. The code within the try block is monitored for exceptions. If an exception occurs, it is caught by the catch block, which contains the code to handle the exception. This prevents the program from terminating abruptly due to an unhandled exception.


46. Explain the concept of method overloading in Java.

Answer:

Method overloading in Java allows a class to have multiple methods with the same name but different parameter lists. This enables a class to provide different versions of a method for different types or numbers of arguments. It improves code readability and maintainability.


47. What is the purpose of encapsulation in Java?

Answer:

Encapsulation is a fundamental concept in object-oriented programming that involves bundling data (attributes) and methods (functions) that operate on the data within a single unit, called a class. It restricts access to some of the object’s components, typically the internal data, from the outside. This protects the integrity of the data and ensures that it is accessed and modified only through well-defined methods.


48. What is a constructor in Java?

Answer:

A constructor is a special method in a Java class that is used to initialize an object. It has the same name as the class and does not have a return type. Constructors are automatically called when an object is created using the new keyword. They are used to set initial values for object attributes and perform other setup tasks.


49. Explain the concept of interfaces in Java.

Answer:

An interface in Java is a reference type that is similar to a class. It is a collection of abstract methods and constant declarations. An interface provides a contract for what a class can do, without specifying how it does it. Classes implement interfaces by providing concrete implementations for all the methods defined in the interface.


50. What is the purpose of the equals method in Java?

Answer:

The equals method in Java is used to compare the content of two objects for equality. By default, it compares object references, but it can be overridden in a class to provide custom comparison logic. This allows objects of a class to define their own notion of equality.


51. Explain the concept of composition in Java.

Answer:

Composition is a design technique in object-oriented programming where a class contains an instance of another class as a member. This allows for building complex relationships between objects. It is often used to represent a “has-a” relationship, where one object has another as part of its state.


52. What is the purpose of the toString method in Java?

Answer:

The toString method is used to obtain a string representation of an object. It is automatically called when an object is concatenated with a string using the + operator or when println is called to print an object. By overriding this method, a class can provide a meaningful string representation of its objects.


53. Explain the concept of packages in Java.

Answer:

Packages in Java are used to organize classes and interfaces into groups. They help prevent naming conflicts and provide a way to control access to class members. A package is a directory that contains a group of related classes and interfaces. It also allows for better modularization and reusability of code.


54. What is the purpose of the static block in Java?

Answer:

The static block in Java is a block of code that is executed when the class is first loaded into memory by the Java Virtual Machine (JVM). It is used to perform one-time initialization tasks for the class, such as setting up static variables or initializing static resources.


55. Explain the concept of method overriding in Java.

Answer:

Method overriding occurs when a subclass provides a specific implementation for a method that is already defined in its superclass. It allows a subclass to provide a specialized implementation of a method, while still maintaining the same method signature. This enables polymorphic behavior, where a method call is resolved at runtime based on the actual object type.


56. What is the purpose of the instanceof operator in Java?

Answer:

The instanceof operator in Java is used to test whether an object is an instance of a particular class or interface. It returns true if the object is an instance of the specified type, or one of its subclasses or subinterfaces. It is often used to perform type checking before type casting.


57. Explain the concept of abstract classes in Java.

Answer:

An abstract class in Java is a class that cannot be instantiated on its own. It serves as a blueprint for other classes that extend it. It may contain abstract methods, which are declared but not implemented in the abstract class. Subclasses must provide concrete implementations for these abstract methods.


58. What is the purpose of the final variable in Java?

Answer:

A final variable in Java is a constant whose value cannot be changed after it is initialized. It must be assigned a value exactly once, either at the time of declaration or in the constructor. Attempting to reassign a final variable will result in a compilation error.


59. Explain the concept of anonymous classes in Java.

Answer:

An anonymous class in Java is a class without a name. It is typically used for one-time use when creating an instance of a class and providing its implementation at the same time. Anonymous classes are declared and instantiated in a single expression and are often used for event handling and callback functions.


60. What is the purpose of the try-catch block in Java?

Answer:

The try-catch block in Java is used for exception handling. The code within the try block is monitored for exceptions. If an exception occurs, it is caught by the catch block, which contains the code to handle the exception. This prevents the program from terminating abruptly due to an unhandled exception.


61. Explain the concept of method overloading in Java.

Answer:

Method overloading in Java allows a class to have multiple methods with the same name but different parameter lists. This enables a class to provide different versions of a method for different types or numbers of arguments. It improves code readability and maintainability.


62. What is the purpose of encapsulation in Java?

Answer:

Encapsulation is a fundamental concept in object-oriented programming that involves bundling data (attributes) and methods (functions) that operate on the data within a single unit, called a class. It restricts access to some of the object’s components, typically the internal data, from the outside. This protects the integrity of the data and ensures that it is accessed and modified only through well-defined methods.


63. What is a constructor in Java?

Answer:

A constructor is a special method in a Java class that is used to initialize an object. It has the same name as the class and does not have a return type. Constructors are automatically called when an object is created using the new keyword. They are used to set initial values for object attributes and perform other setup tasks.


64. Explain the concept of interfaces in Java.

Answer:

An interface in Java is a reference type that is similar to a class. It is a collection of abstract methods and constant declarations. An interface provides a contract for what a class can do, without specifying how it does it. Classes implement interfaces by providing concrete implementations for all the methods defined in the interface.


65. What is the purpose of the equals method in Java?

Answer:

The equals method in Java is used to compare the content of two objects for equality. By default, it compares object references, but it can be overridden in a class to provide custom comparison logic. This allows objects of a class to define their own notion of equality.


66. Explain the concept of composition in Java.

Answer:

Composition is a design technique in object-oriented programming where a class contains an instance of another class as a member. This allows for building complex relationships between objects. It is often used to represent a “has-a” relationship, where one object has another as part of its state.


67. What is the purpose of the toString method in Java?

Answer:

The toString method is used to obtain a string representation of an object. It is automatically called when an object is concatenated with a string using the + operator or when println is called to print an object. By overriding this method, a class can provide a meaningful string representation of its objects.


68. Explain the concept of packages in Java.

Answer:

Packages in Java are used to organize classes and interfaces into groups. They help prevent naming conflicts and provide a way to control access to class members. A package is a directory that contains a group of related classes and interfaces. It also allows for better modularization and reusability of code.


69. What is the purpose of the static block in Java?

Answer:

The static block in Java is a block of code that is executed when the class is first loaded into memory by the Java Virtual Machine (JVM). It is used to perform one-time initialization tasks for the class, such as setting up static variables or initializing static resources.


70. Explain the concept of method overriding in Java.

Answer:

Method overriding occurs when a subclass provides a specific implementation for a method that is already defined in its superclass. It allows a subclass to provide a specialized implementation of a method, while still maintaining the same method signature. This enables polymorphic behavior, where a method call is resolved at runtime based on the actual object type.


71. What is the purpose of the instanceof operator in Java?

Answer:

The instanceof operator in Java is used to test whether an object is an instance of a particular class or interface. It returns true if the object is an instance of the specified type, or one of its subclasses or subinterfaces. It is often used to perform type checking before type casting.


72. Explain the concept of abstract classes in Java.

Answer:

An abstract class in Java is a class that cannot be instantiated on its own. It serves as a blueprint for other classes that extend it. It may contain abstract methods, which are declared but not implemented in the abstract class. Subclasses must provide concrete implementations for these abstract methods.


73. What is the purpose of the final variable in Java?

Answer:

A final variable in Java is a constant whose value cannot be changed after it is initialized. It must be assigned a value exactly once, either at the time of declaration or in the constructor. Attempting to reassign a final variable will result in a compilation error.


74. Explain the concept of anonymous classes in Java.

Answer:

An anonymous class in Java is a class without a name. It is typically used for one-time use when creating an instance of a class and providing its implementation at the same time. Anonymous classes are declared and instantiated in a single expression and are often used for event handling and callback functions.


75. What is the purpose of the try-catch block in Java?

Answer:

The try-catch block in Java is used for exception handling. The code within the try block is monitored for exceptions. If an exception occurs, it is caught by the catch block, which contains the code to handle the exception. This prevents the program from terminating abruptly due to an unhandled exception.


76. Explain the concept of method overloading in Java.

Answer:

Method overloading in Java allows a class to have multiple methods with the same name but different parameter lists. This enables a class to provide different versions of a method for different types or numbers of arguments. It improves code readability and maintainability.


77. What is the purpose of encapsulation in Java?

Answer:

Encapsulation is a fundamental concept in object-oriented programming that involves bundling data (attributes) and methods (functions) that operate on the data within a single unit, called a class. It restricts access to some of the object’s components, typically the internal data, from the outside. This protects the integrity of the data and ensures that it is accessed and modified only through well-defined methods.


78. What is a constructor in Java?

Answer:

A constructor is a special method in a Java class that is used to initialize an object. It has the same name as the class and does not have a return type. Constructors are automatically called when an object is created using the new keyword. They are used to set initial values for object attributes and perform other setup tasks.


79. Explain the concept of interfaces in Java.

Answer:

An interface in Java is a reference type that is similar to a class. It is a collection of abstract methods and constant declarations. An interface provides a contract for what a class can do, without specifying how it does it. Classes implement interfaces by providing concrete implementations for all the methods defined in the interface.


80. What is the purpose of the equals method in Java?

Answer:

The equals method in Java is used to compare the content of two objects for equality. By default, it compares object references, but it can be overridden in a class to provide custom comparison logic. This allows objects of a class to define their own notion of equality.


81. Explain the concept of composition in Java.

Answer:

Composition is a design technique in object-oriented programming where a class contains an instance of another class as a member. This allows for building complex relationships between objects. It is often used to represent a “has-a” relationship, where one object has another as part of its state.


82. What is the purpose of the toString method in Java?

Answer:

The toString method is used to obtain a string representation of an object. It is automatically called when an object is concatenated with a string using the + operator or when println is called to print an object. By overriding this method, a class can provide a meaningful string representation of its objects.


83. Explain the concept of packages in Java.

Answer:

Packages in Java are used to organize classes and interfaces into groups. They help prevent naming conflicts and provide a way to control access to class members. A package is a directory that contains a group of related classes and interfaces. It also allows for better modularization and reusability of code.


84. What is the purpose of the static block in Java?

Answer:

The static block in Java is a block of code that is executed when the class is first loaded into memory by the Java Virtual Machine (JVM). It is used to perform one-time initialization tasks for the class, such as setting up static variables or initializing static resources.


85. Explain the concept of method overriding in Java.

Answer:

Method overriding occurs when a subclass provides a specific implementation for a method that is already defined in its superclass. It allows a subclass to provide a specialized implementation of a method, while still maintaining the same method signature. This enables polymorphic behavior, where a method call is resolved at runtime based on the actual object type.


86. What is the purpose of the instanceof operator in Java?

Answer:

The instanceof operator in Java is used to test whether an object is an instance of a particular class or interface. It returns true if the object is an instance of the specified type, or one of its subclasses or subinterfaces. It is often used to perform type checking before type casting.


87. Explain the concept of abstract classes in Java.

Answer:

An abstract class in Java is a class that cannot be instantiated on its own. It serves as a blueprint for other classes that extend it. It may contain abstract methods, which are declared but not implemented in the abstract class. Subclasses must provide concrete implementations for these abstract methods.


88. What is the purpose of the final variable in Java?

Answer:

A final variable in Java is a constant whose value cannot be changed after it is initialized. It must be assigned a value exactly once, either at the time of declaration or in the constructor. Attempting to reassign a final variable will result in a compilation error.


89. Explain the concept of anonymous classes in Java.

Answer:

An anonymous class in Java is a class without a name. It is typically used for one-time use when creating an instance of a class and providing its implementation at the same time. Anonymous classes are declared and instantiated in a single expression and are often used for event handling and callback functions.


90. What is the purpose of the try-catch block in Java?

Answer:

The try-catch block in Java is used for exception handling. The code within the try block is monitored for exceptions. If an exception occurs, it is caught by the catch block, which contains the code to handle the exception. This prevents the program from terminating abruptly due to an unhandled exception.


91. Explain the concept of method overloading in Java.

Answer:

Method overloading in Java allows a class to have multiple methods with the same name but different parameter lists. This enables a class to provide different versions of a method for different types or numbers of arguments. It improves code readability and maintainability.


92. What is the purpose of encapsulation in Java?

Answer:

Encapsulation is a fundamental concept in object-oriented programming that involves bundling data (attributes) and methods (functions) that operate on the data within a single unit, called a class. It restricts access to some of the object’s components, typically the internal data, from the outside. This protects the integrity of the data and ensures that it is accessed and modified only through well-defined methods.


93. What is a constructor in Java?

Answer:

A constructor is a special method in a Java class that is used to initialize an object. It has the same name as the class and does not have a return type. Constructors are automatically called when an object is created using the new keyword. They are used to set initial values for object attributes and perform other setup tasks.


94. Explain the concept of interfaces in Java.

Answer:

An interface in Java is a reference type that is similar to a class. It is a collection of abstract methods and constant declarations. An interface provides a contract for what a class can do, without specifying how it does it. Classes implement interfaces by providing concrete implementations for all the methods defined in the interface.


95. What is the purpose of the equals method in Java?

Answer:

The equals method in Java is used to compare the content of two objects for equality. By default, it compares object references, but it can be overridden in a class to provide custom comparison logic. This allows objects of a class to define their own notion of equality.


96. Explain the concept of composition in Java.

Answer:

Composition is a design technique in object-oriented programming where a class contains an instance of another class as a member. This allows for building complex relationships between objects. It is often used to represent a “has-a” relationship, where one object has another as part of its state.


97. What is the purpose of the toString method in Java?

Answer:

The toString method is used to obtain a string representation of an object. It is automatically called when an object is concatenated with a string using the + operator or when println is called to print an object. By overriding this method, a class can provide a meaningful string representation of its objects.


98. Explain the concept of packages in Java.

Answer:

Packages in Java are used to organize classes and interfaces into groups. They help prevent naming conflicts and provide a way to control access to class members. A package is a directory that contains a group of related classes and interfaces. It also allows for better modularization and reusability of code.


99. What is the purpose of the static block in Java?

Answer:

The static block in Java is a block of code that is executed when the class is first loaded into memory by the Java Virtual Machine (JVM). It is used to perform one-time initialization tasks for the class, such as setting up static variables or initializing static resources.


100. Explain the concept of method overriding in Java.

Answer:

Method overriding occurs when a subclass provides a specific implementation for a method that is already defined in its superclass. It allows a subclass to provide a specialized implementation of a method, while still maintaining the same method signature. This enables polymorphic behavior, where a method call is resolved at runtime based on the actual object type.