1) What is Abstract class in Java?
Ans:-Abstract Classes are classes
in Java that declare one or more abstract methods. A method without body (no implementation) is known as
abstract method.
2) Write a Java Program,
which has get the type of bike from the user based on user input it has to call
related class?
Ans:-
import java.util.Scanner;
abstract class bike
{
bike()
{
System.out.println("bike
is created");
}
abstract void run();
void changegear()
{
System.out.println("gear
changed");
}
}
class honda extends bike
{
void run()
{
System.out.println("honda");
}
}
class unicorn extends bike
{
void run()
{
System.out.println("unicorn");
}
}
class test2
{
public static void
main(String args[])
{
Scanner in=new
Scanner(System.in);
System.out.println("enter
your choice");
int choice=in.nextInt();
switch(choice)
{
case 1:
{
bike obj=new honda();
obj.run();
obj.changegear();
break;
}
case 2:
{
bike obj=new unicorn();
obj.run();
obj.changegear();
break;
}
}
}
}
3) Write a java program to
print Good Morning, Good Afternoon, And Good Evening based on the Date Time?
Ans:-
import
java.util.GregorianCalendar;
public class DisplayDateTime
{
public static void main(String[] args)
{
GregorianCalendar time = new
GregorianCalendar();
int hour = time.get(Calendar.HOUR_OF_DAY);
int min = time.get(Calendar.MINUTE);
int day = time.get(Calendar.DAY_OF_MONTH);
int month = time.get(Calendar.MONTH) + 1;
int year = time.get(Calendar.YEAR);
System.out.println("The current time is
\t" + hour + ":" + min);
System.out.println("Today's date is
\t" + month + "/" + day + "/" + year);
if (hour < 12)
System.out.println("Good
Morning!");
else if (hour < 17 && !(hour ==
12))
System.out.println("Good
Afternoon");
else if (hour == 12)
System.out.println("Good Noon");
else
System.out.println("Good
Evening");
}
}
4)Write a java Program to
count the number of digit?
Ans:-
class noofdigit
{
public static void
main(String args[])
{
int number,count=0;
Scanner sc=new
Scanner(System.in);
System.out.println("Please
Enter any number");
number=sc.nextInt();
while(number>0)
{
number=number/10;
count=count+1;
}
System.out.println("no
of digit"+count);
}
}
5) What are the basic
interfaces of Java Collections Framework?
Ans:- Set, List, Map, Queue, Iterator,SortedMap, List
Iterator
6) What are the rules for
declaring Java Identifier?
Ans:-
1) Identifier Should not start with the digit
2) Java identifier are case sensitive of course java language
3) There Is no length limit for identifiers but it is not
Recommended to take too lengthy identifier.
4) Reserved Keyword should
not used a Identifier.
7) What are the different
types of Comment available in Java?
Ans:-
(i)Single line Comment
(ii)Multi line Comment
(iii)Documentation Comment
8) What is the difference
between Overloading and Overriding in JAVA?
Ans:-
Overloading:
Methods are said to be
overloading when many method in a class have same name but different argument.
Overriding:
While Inherting,If method
name in the base class and derived class are same, Then contents in the derived
class are override by method in base class is Overloading.
10) Define Package in Java?
Ans:-Packages are nothing
directory of our file system that exist our file system they contain a set of
class file.
11)List 5 important things
to connect Java applications with MySQL?
Ans:-
(i)Driver Class
(ii)JDBC Connection URL
(iii)Username
(iv)Password
(v)Jar File
12) What are the different
OOPS concept in Java?
Ans:-Class, Inheritance, Objects,
Abstraction, Encapsulation, Polymorphism.
13) What is Inheritance?
Ans:- Inheritance is the mechanism
of deriving a new class from an oldclass.Here the old class is called as Base
class and new class is called as Derived Class.
14) What is Static Binding
and Dynamic Binding?
Ans:- Static or early binding is
resolved at compile time. Method overloading is an example of static binding.
Dynamic or late or virtual binding is resolved at run time. Method overriding
is an example of dynamic binding.
15) Define Class and Object
in Java?
Ans:-Class is a way to bind
member variables and member functions together. By creating object we can
access member variable and member functions in the class.
16)Write a Java program to
implement emp details using class and object?
Ans:-
Emp details using Classes and Objects:
import java.util.Scanner;
class employee
{
String empname;
int empid;
double emphone;
String empaddress;
void getdata()
{
Scanner sc=new
Scanner(System.in);
System.out.println("enter
empname");
empname=sc.next();
System.out.println("enter
empid");
empid=sc.nextInt();
System.out.println("enter
empphoneno");
emphone=sc.nextInt();
System.out.println("enter
employee address");
empaddress=sc.next();
}
void putdata()
{
Scanner sc=new
Scanner(System.in);
System.out.println("empname="+empname);
System.out.println("empid="+empid);
System.out.println("empname="+emphone);
System.out.println("empaddres="+empaddress);
}
}
class test
{
public static void
main(String args[])
{
employee e1=new employee();
e1.getdata();
e1.putdata();
}
}
17)Can you change the above
program to get n number of employee records?
Ans:-
import java.util.Scanner;
class employee
{
String empname;
int empid;
double emphone;
String empaddress;
void getdata()
{
Scanner sc=new
Scanner(System.in);
System.out.println("enter
empname");
empname=sc.next();
System.out.println("enter
empid");
empid=sc.nextInt();
System.out.println("enter
empphoneno");
emphone=sc.nextInt();
System.out.println("enter
employee address");
empaddress=sc.next();
}
void putdata()
{
Scanner sc=new
Scanner(System.in);
System.out.println("empname="+empname);
System.out.println("empid="+empid);
System.out.println("empname="+emphone);
System.out.println("empaddres="+empaddress);
}
}
class test1
{
public static void
main(String args[])
{
employee[] e1=new
employee[10];
Scanner sc=new
Scanner(System.in);
int i,n;
System.out.println("Enter
how many records to store");
n=sc.nextInt();
for(i=1;i<=n;i++)
e1[i] =
new employee(); // Allocating
memory to each object
for(i=1;i<=n;i++)
{
e1[i].getdata();
}
for(i=1;i<=n;i++)
{
e1[i].putdata();
}
}
}
18) What is Path Variable in
Java?
Ans:- The PATH variable gives the
location of executable like javac, java etc. It is possible to run a program
without specifying the PATH but you will need to give full path of executable
like C:\Program Files\Java\jdk1.8.0_131\bin\javac A.java instead of simple
javac A.java.
19) Write any 3 data type
declaration with examples?
Ans:-Assume that we are using Scanner class for
implementation:
Scanner sc=new Scanner(System.in);
String Data type Declaration example:
String empname;
empname=sc.next();
Integer Data type Declaration Example:
int empid;
empid=sc.nextInt();
Double Data type Declaration Example:
Double fee;
fee=sc.nextDouble();
(or)
double fee=sc.nextDouble();
20) How to create an Array?
Ans:-
An Array is declared similar
to how a variable is declared, but we need to add [] after the type.
Example:
int [] intArray;
String [] stringArray;
MyClass [] myClassArray;
Or
int[] age;
age = new int[5];
21) Can we change the size of an
array at run time?
Ans:- No we cannot change the
array size. Though there are similar data types available which allow a change
in size.
22) What is the default
value of Array?
Ans:-Any new Array is always
initialized with a default value as follows
For byte, short, int, long –
default value is zero (0).
For float, double – default
value is 0.0.
For Boolean – default value
is false.
For object – default value
is null.
23) Can we add or delete an
element after assigning an array?
Ans:-No it is not possible.