→ An object can be a variable, a data structure, a function, or a method, and as such, is a value in memory referenced by an identifier.
→ In the class based object-oriented programming paradigm, object refers to a particular instance of a class, where the object can be a combination of variables, functions, and data structures.
→ An object has state, exhibits some well defined behavior, and has a unique identity.

The Throwable class is the superclass of all errors and exceptions in the Java language.

→ It is nothing but multilevel inheritance.
→ If a class C is derived from class B, which is derived from class A, all through public inheritance, then a class C member function can access public and protected data of A and B and all data of C

Java does not - unlike C - interpret 0 as false and 1 as true.
So we cannot use integers in the while() statement.
So line number 6 will give syntax error.

→ The static storage class instructs the compiler to keep a local variable in existence during the life-time of the program instead of creating and destroying it each time it comes into and goes out of scope. Therefore, making local variables static allows them to maintain their values between function calls.
→ The static modifier may also be applied to global variables. When this is done, it causes that variable's scope to be restricted to the file in which it is declared.
→ In C programming, when static is used on a global variable, it causes only one copy of that member to be shared by all the objects of its class.

A constructor cannot specify any return type, not even void. A constructor cannot be final, static or abstract.

Generalization--> "is a kind of" relationship. It is used for object oriented inheritance models.
Aggregation-->"Has a" relationship

● A control structure is a block of programming that analyzes variables and chooses a direction in which to go based on given parameters.
● The term flow control details the direction the program takes (which way program control "flows").
● Hence it is the basic decision-making process in computing; flow control determines how a computer will respond when given certain conditions and parameters.

● Object-oriented design is the process of planning a system of interacting objects for the purpose of solving a software problem.
● An object contains encapsulated data and procedures (operations) grouped together to represent an entity. The 'object interface' defines how the object can be interacted with.

We can’t directly assign the base class members by using​ ​ initializer list​ in the derived class
We should call the base class constructor in order to initialize base class members.

● C++ constructor call order will be from top to down that is from base class to derived class and c++ destructor call order will be in reverse order.
● First child class and later parent class.

Option -4 false because new package is created by using syntax package package_name which is user defined .There is no relation with class name.

● An abstract class can have an abstract method without body and it can have methods with implementation also. ● Multiple inheritance is not possible with abstract classes.

● The interface in java is a blueprint of a class. It has static constants and abstract methods.
● There can be only abstract methods in the Java interface, not method body.
● It cannot be instantiated just like the abstract class because there is no method definition available with the interface.

→ The purpose of any analysis activity in the software life cycle is to create a model of the system's functional requirements that is independent of implementation constraints.
→ The main difference between object-oriented analysis and other forms of analysis is that by the object-oriented approach we organize requirements around objects, which integrate both behaviors (processes) and states (data) modeled after real world objects that the system interacts with. In other or traditional analysis methodologies, the two aspects: processes and data are considered separately.
→ For example, data may be modeled by ER diagrams, and behaviors by flow charts or structure charts.

If null were an Object, it would support the methods of java.lang.Object such as equals().
However, this is not the case - any method invocation on a null results in a NullPointerException.
There is also a special null type, the type of the expression null, which has no name. Because the null type has no name, it is impossible to declare a variable of the null type or to cast to the null type. The null reference is the only possible value of an expression of null type. The null reference can always be cast to any reference type. In practice, the programmer can ignore the null type and just pretend that null is merely a special literal that can be of any reference type

A low level event that indicates that a window has changed its status. This low-level event is generated by a Window object when it is opened, closed, activated, deactivated, iconified, or deiconified, or when focus is transferred into or out of the Window.

(1) and (2) are both valid constructors for Thread.
(3), (4), and (5) are not legal Thread constructors

● An active object is one that encompasses its own thread of control.
● Active objects are generally autonomous, meaning that they exhibit some behaviour without being operated upon by another object
● Passive objects can only undergo a state change when explicitly acted upon

Encapsulation is the mechanism that binds together code and data it manipulates, and keeps both safe from outside interface and misuse. Class, which contains data members and methods is used to implement Encapsulation.

→ Destructors are used to de-allocate the memory that has been allocated for the object by the constructor.
→ Unlike constructor a destructor neither takes any arguments nor does it returns value. And destructor can’t be overloaded.

→ In Run time Polymorphism, call is not resolved by the compiler.
→ Run time Polymorphism is achieved by virtual functions and pointers.
→ Compile time Polymorphism achieved by function overloading and operator overloading.

→ A virtual function or virtual method is an inheritable and overridable function or method for which dynamic dispatch is facilitated.
→ A pure virtual function or pure virtual method is a virtual function that is required to be implemented by a derived class if the derived class is not abstract.

→ A virtual function or virtual method is an inheritable and overridable function or method for which dynamic dispatch is facilitated.
→ Dynamic binding occurs when a pointer or reference is associated with a member function based on the dynamic type of the object.
→ The member function that is dynamically bound must override a virtual function declared in a direct or indirect base class.

→ A catch block is where you handle the exceptions, this block must follow the try block.
→ A single try block can have several catch blocks associated with it. You can catch different exceptions in different catch blocks.
→ When an exception occurs in try block, the corresponding catch block that handles that particular exception executes

→ x%=2; is not the same as x=x/2;
→ x%=2; is the same as x=x%2;

We can’t used the keyword “while” as class name.So it will give syntax error.

public class Object:
Class Object is the root of the class hierarchy. Every class has Object as a superclass. All objects, including arrays, implement the methods of this class.

→ Public Inheritance − When deriving a class from a public base class, public members of the base class become public members of the derived class and protected members of the base class become protected members of the derived class.
→ A base class's private members are never accessible directly from a derived class, but can be accessed through calls to the public and protected members of the base class. We can summarize the different access types according to - who can access them in the following way −

→ An escape sequence is a sequence of characters that does not represent itself when used inside a character or string literal, but is translated into another character or a sequence of characters that may be difficult or impossible to represent directly.
→ All escape sequences consist of two or more characters, the first of which is the backslash, \ (called the "Escape character"); the remaining characters determine the interpretation of the escape sequence. For example, \n is an escape sequence that denotes a newline character.
→ If we treat it a character constant means one character
Note: An escape sequence is regarded as a single character and is therefore valid as a character constant.

Two or more functions having same name but different argument(s) are known as overloaded functions. So option is not true.

→ Student S1:----whenever we create object to the class , automatically default constructor will be called.
→ Student S2=S1:------The copy constructor is a constructor which creates an object by initializing it with an object of the same class, which has been created previously.

● JVM is a engine that provides runtime environment to drive the Java Code or applications. It converts Java bytecode into machines language.
● First, Java code is compiled into bytecode. This bytecode gets interpreted on different machines

→ The attributes of student class are name and marks.
→ There are two objects created in the above program and both have same attributes.

All the wrapper classes (Integer, Long, Byte, Double, Float, Short) are subclasses of the abstract class Number.

●The argument list should be exactly the same as that of the overridden method.
● The return type should be the same or a subtype of the return type declared in the original overridden method in the superclass.

●Data hiding is a software development technique specifically used in object-oriented programming (OOP) to hide internal object details (data members). Data hiding ensures exclusive data access to class members and protects object integrity by preventing unintended or intended changes.
● Data abstraction refers to providing only essential information to the outside world and hiding their background details, i.e., to represent the needed information in program without presenting the details.
● Encapsulation is a process of combining data members and functions in a single unit called class. This is to prevent the access to the data directly, the access to them is provided through the functions of the class.

Languages that support object oriented programming typically use inheritance for code reuse and extensibility in the form of either classes or prototypes. Those that use classes support two main concepts:
1. Classes – the definitions for the data format and available procedures for a given type or class of object; may also contain data and procedures (known as class methods) themselves, i.e. classes contain the data members and member functions
2. Objects – instances of classes

True: point' is the base class and 'circle' is the derived class
True: The colon(:) in the header of class definition indicates inheritance
True: The keyword 'public' indicates type of inheritance
False: All the public and protected members of class 'circle' are inherited as public and protected members respectively into class point.

→ In question they are clearly mentioned that 4 rows and 5 columns.
→ ​ Syntax int array[ ] [ ]=new int[row size][column size];
(or)
int[ ] [ ] array=new int[row size][column size];
So, Option D is correct answer.

Garbage collection is happened when all references to an object are going, then the memory used by the object is automatically reclaimed

Integer data type we are using X.length and character data type we are using function X.length().
→ array.length : length is a final variable applicable for arrays. With the help of length variable, we can obtain the size of the array.
→ string.length() : length() method is a final variable which is applicable for string objects. length() method returns the number of characters presents in the string.

→ Multiple inheritance is a feature of some object-oriented computer programming languages in which an object or class can inherit characteristics and features from more than one parent object or parent class. It is distinct from single inheritance, where an object or class may only inherit from one particular object or class.

→ Java is a strongly typed programming language because every variable must be declared with a data type. A variable cannot start off life without knowing the range of values it can hold, and once it is declared, the data type of the variable cannot change.

The possible values are either integer constant or character constant.No other data type values are allowed.

→The java.lang.Math.max(int a, int b) returns the greater of two int values.
→We can find the greater of any two data types variables.
→Option C consists of four variables , So it is invalid.

In the c++ (or) C programming language , in order to use the variables in the program we must declare the variables before using.

The following table shows the access to members permitted by each modifier.

The following table shows the access to members permitted by each modifier.

When a class is derived from a class which is also derived from another class, i.e. a class having more than one parent classes, such inheritance is called Multilevel Inheritance.

→A class in C++ is a user defined type or data structure declared with keyword class that has data and functions (also called methods) as its members whose access is governed by the three access specifiers private, protected or public (by default access to members of a class is private).
→The private members are not accessible outside the class; they can be accessed only through methods of the class. The public members form an interface to the class and are accessible outside the class.

→ A friend function of a class is defined outside that class' scope but it has the right to access all private and protected members of the class. Even though the prototypes for friend functions appear in the class definition, friends are not member functions.
TRUE: function can only be declared a friend by a class itself.
TRUE: Friend functions are not members of a class, they are associated with it.
FALSE:Friend functions are members of a class.
TRUE: It can have access to all members of the class, even private ones.

→ When a class grants friend status to another class all member functions of the class granted friendship have unrestricted access to the members of the class granting the friendship.
→ Although the entire second class must be a friend to the first class, you can select which functions in the first class will be friends of the second class.

→ When a method in a subclass has the same name and type signatures as a method in the superclass, then the method in the subclass overrides the method in the superclass.

→ A publicly derived class is a subtype of its base class.
→ Inheritance is defined as deriving new classes (sub classes) from existing ones (super class or base class) and forming them into a hierarchy of classes.
→ Inheritance allows programmers to create classes that are built upon existing classes, to specify a new implementation while maintaining the same behaviors (realizing an interface), to reuse code and to independently extend original software via public classes and interfaces.

In some cases, the exception handling mechanism fails and a call to void terminate() is made. This terminate() call occurs in any of the following situations:
The exception handling mechanism cannot find a handler for a thrown exception. The following cases are more specific:
1. During stack unwinding, a destructor throws an exception and that exception is not handled.
2. The expression that is thrown also throws an exception, and that exception is not handled.
3. The constructor or destructor of a nonlocal static object throws an exception, and the exception is not handled.
4. A function registered with atexit() throws an exception, and the exception is not handled. The following demonstrates this:
A throw expression without an operand tries to rethrow an exception, and no exception is presently being handled.

First we will create the object of simple class.
By using object , we call the function start().
In the start() function definition, first statement is integer array with three elements.
long [ ] Q= method (P); Again function method(p) will be called.
In the definition of method function, we are changing the second element of array to value 7 and returning updated array to array Q.
We are passing address of P as argument to method so Modifications happened in the method automatically reflects to array P.
Both array P and Q consists of values {3,7,5}
The sum of the three values are 15

● If a class has multiple methods having same name but different in parameters, it is known as Method Overloading.Method Overloading is a feature that allows a class to have more than one method having the same name, if their argument lists are different.So the option-3 is False.
● The final keyword in java is used to restrict the user. The java final keyword can be used in many context. Final can be: variable, method and class.
● A Java class can only extend one parent class. Multiple inheritance (extends) is not allowed. Interfaces are not classes, however, and a class can implement more than one interface.

FALSE: Constants that cannot be changed are declared using the ‘static’ keyword.
TRUE: A class can only inherit one class but can implement multiple interfaces.

Statement-I and II are TRUE
A class which is declared as abstract is known as an abstract class. It can have abstract and non-abstract methods. It needs to be extended and its method implemented. It cannot be instantiated.
Rules:
1. An abstract class must be declared with an abstract keyword.
2. It can have abstract and non-abstract methods.
3. It cannot be instantiated.
4. It can have constructors and static methods also.
5. It can have final methods which will force the subclass not to change the body of the method.

Method overriding can be prevented by using final as a modifier at the start of method declaration.

A class which is declared as abstract is known as an abstract class. It can have abstract and non-abstract methods. It needs to be extended and its method implemented. It cannot be instantiated.
Rules:
1. An abstract class must be declared with an abstract keyword.
2. It can have abstract and non-abstract methods.
3. It cannot be instantiated.
4. It can have constructors and static methods also.
5. It can have final methods which will force the subclass not to change the body of the method.

→ Java uses threads to enable the entire environment to be asynchronous.
→ Synchronous (or) Synchronized means "connected", or "dependent" in some way. In other words, two synchronous tasks must be aware of one another, and one task must execute in some way that is dependent on the other, such as wait to start until the other task has completed.
→ Asynchronous means they are totally independent and neither one must consider the other in any way, either in initiation or in execution.

Static variables→ Fortran 77

Stack dynamic→ Local variables in Pascal

Explicit heap dynamic→ All objects in JAVA

Implicit heap dynamic→ All variables in APL

Implicit return type of a class constructor is class type itself.

Syntax For Constructors:

Access_Modifier No Return_Type Class(...)

Example:

public static main(String [ ]args)

Constructor rules:

1. Constructors are always used with a new.

2. Have the same name as that of Class

3. Does not have a return type

4. Can be Overloaded but not Overridden.

Nested classes are divided into two categories:

1. Static

2. Non static.

Nested classes that are declared static are simply called static nested classes.

Non static nested classes are called inner classes.

• Abstract class may consist of at least one abstract method.

• Abstract method means method without body, we can also be called as pure virtual functions.

• If a class is marked with keyword abstract then it is called an abstract class. It can NOT be instantiated by using new operator. But an abstract class can be used as the superclass reference for the subclass object.

• Abstract classes, by design, are not complete or functional. They are meant to serve as a base from which complete classes can be built, by aggregating the common members and methods that they all will need into an abstract base class, and then allowing the inheriting classes to fill out the necessary details. So abstract class can’t be instantiated

• A reference variable is an alias, that is, another name for an already existing variable. Once a reference is initialized with a variable, either the variable name or the reference name may be used to refer to the variable.

• A reference variable must be initialized at the time of declaration.

→ Dynamic programming language is a class of high-level programming languages which, at runtime, execute many common programming behaviors that static programming languages perform during compilation. These behaviors could include extension of the program, by adding new code, by extending objects and definitions, or by modifying the type system.
→ Ada is a structured, statically typed, imperative, and object-oriented high-level computer programming language, extended from Pascal and other languages.
→ Prolog is a logic programming language associated with artificial intelligence and computational linguistics. Prolog is intended primarily as a declarative programming language: the program logic is expressed in terms of relations, represented as facts and rules.
→ Python is dynamically typed and garbage-collected. It supports multiple programming paradigms, including procedural, object-oriented, and functional programming

Abstract class may consist of at least one abstract method.
Abstract method means method without body, we can also be called as pure virtual functions.

Polymorphism: Polymorphism means many forms. It is used to perform similar operations to do similar things.
Inheritance: It is the process of creating new classes(derived class) from existing classes( base class) by inheriting their properties into derived class.
Encapsulation:It is the process of Picking both operator and attributes with operations appropriate to model an object
Abstraction: Abstraction refers to the process of Hiding implementation details of methods from users of objects

Statement (a) is true.
An abstract class may or may not have abstract methods so that it may provide the complete and default code.