Part 5
Basic Java Interview Questions and Answers covered in this post:
What is Widening?
-
When we assign a value of a smaller data type to a bigger
data type.
-
It is possible when two data types are compatible.
-
Widening Scope:
byte -> short -> int -> long -> float -> double.
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package simplifiedjava.crackedInterview; public class WideningDemo {
public
static
void
main(String[] args) {
int
i=100;
long
j
= i;
float
k
= j;
float
k1
= i;
System.out.println("Value of i = "+ i
+ " \nValue of j = "+ j
+ "\nValue of k = "+ k
+ "\nValue of k1 = "+ k1);
}
} |
What is Narrowing?
-
When we assign a value of a bigger data type to a smaller
data type.
-
It is possible when two data types are compatible.
-
Narrowing Scope:
byte <- short <- int <- long <- float <- double.
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package simplifiedjava.crackedInterview; public class WideningDemo {
public
static
void
main(String[] args) {
float
i=100;
long
j
= (long) i;
int
k
= (int) j;
int
k1
= (int) i;
System.out.println("Value of i = "+ i
+ " \nValue of j = "+ j
+ "\nValue of k = "+ k
+ "\nValue of k1 = "+ k1);
}
} |
3.
 
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What is equals() and hashcode()
contract?
-
If the two objects are equal then they should have the same
hashcode and if two objects are not equal then they may or may not have the
same hashcode.
-
Objet1.equals(Object2) if true then hashcode must be same of
both objects.
-
Object1.equals(Object2) if false then hashcode may be or may
not be same.
-
As per the oracle documentation, both methods should be
overridden to get the complete equality mechanism you must override equals()
and hashcode() methods.
What is Comparable and Comparator? What
is the difference between Comparable and Comparator?
-
Comparable and Comparator are interfaces that can be used for
sorting purposes.
-
Comparable interface can be used for natural sorting
order.
-
Comparator interface can be used to customize sorting
orders.
-
Comparable has compareTo() method.
-
Comparator has compare() method.
Can you write a code to customize Employee Sorting order by Salary or Designation?
|
package simplifiedjava.crackedInterview; import java.util.Comparator; public class Employee {
private
String empName;
private
String dept;
private
Double salary; private String designation;
public
Employee(String empName, String dept, Double salary, String designation) {
super();
this.empName
= empName;
this.dept
= dept;
this.salary
= salary;
this.designation
= designation;
}
public
Employee(String empName) {
this.empName
= empName;
}
public
String getEmpName() {
return
empName;
}
public
String getDept() {
return
dept;
}
public
void
setDept(String dept) {
this.dept
= dept;
}
public
Double getSalary() {
return
salary;
}
public
void
setSalary(Double salary) {
this.salary
= salary;
}
public
String getDesignation() {
return
designation;
}
public
void
setDesignation(String designation) {
this.designation
= designation;
}
public
void
setEmpName(String empName) {
this.empName
= empName;
}
@Override
public
String toString() {
return
"Employee [empName="
+ empName
+ ", dept="
+ dept
+ ", salary="
+ salary
+ ", designation="
+ designation
+ "]";
}
} package simplifiedjava.crackedInterview; import java.util.Comparator; public class SortEmployeeBySalary implements Comparator<Employee>{
public
int
compare(Employee e1, Employee e2) {
return
e1.getSalary().compareTo(e2.getSalary());
}
} package simplifiedjava.crackedInterview;
import
java.util.ArrayList; import java.util.List; public class ComparableAndComparatorDemo { public static void main(String[] args) {
List<Employee> empList
= new
ArrayList<Employee>();
empList.add(new
Employee("Yogesh","IT",100000.00,"System Analyst"));
empList.add(new
Employee("Arpita","Mangement",1200000.00,"Trustee"));
empList.add(new
Employee("Shweta","DevOps",45000.00,"Jenkin Engineer"));
empList.add(new
Employee("Shruti","IT",65000.00,"DB Admin"));
empList.add(new
Employee("Priyanka","IT",35000.00,"Test Engineer"));
System.out.println("=========== Employee Before Sorting =========="); System.out.println(empList);
System.out.println("======== Employee After Sorting =======");
empList.sort(new
SortEmployeeBySalary());
System.out.println(empList);
} }
Output:
=================== Employee Before Sorting
=====================
[Employee [empName=Yogesh, dept=IT, salary=100000.0,
designation=System Analyst], Employee [empName=Arpita,
dept=Mangement, salary=1200000.0, designation=Trustee], Employee
[empName=Shweta, dept=DevOps, salary=45000.0, designation=Jenkin
Engineer], Employee [empName=Shruti, dept=IT, salary=65000.0,
designation=DB Admin], Employee [empName=Priyanka, dept=IT,
salary=35000.0, designation=Test Engineer]]
=================== Employee After Sorting
=====================
[Employee [empName=Priyanka, dept=IT, salary=35000.0,
designation=Test Engineer], Employee [empName=Shweta, dept=DevOps,
salary=45000.0, designation=Jenkin Engineer], Employee
[empName=Shruti, dept=IT, salary=65000.0, designation=DB Admin],
Employee [empName=Yogesh, dept=IT, salary=100000.0,
designation=System Analyst], Employee [empName=Arpita,
dept=Mangement, salary=1200000.0, designation=Trustee]]
|
What is ENUM? What is the purpose of
ENUM?
-
Enum stands for Enumeration.
-
Enum is a data type that is a set of constants.
-
Enum can be declared inside or outside the class.
-
Please refer to the below example for enum
implementation.
|
package simplifiedjava.crackedInterview; public class EnumDemo { public enum months {JANURAY,FEBRUARY,MAR,APRIL,MAY,JUNE,JULY,AUGUST,SEPTEBER,OCTOBER,NOVEMBER,DECEMER};
public
static
void
main(String[] args) {
for(MONTHS month
: months.values()) {
System.out.print(" "+ month);
}
}
}
Output: JANURAY FEBRUARY MAR APRIL MAY JUNE JULY AUGUST SEPTEBER OCTOBER
NOVEMBER DECEMER |
- Java interview questions and answers all MNC - Click here
- Basic core java interview questions and answers for freshers - Click here
- Core java interview questions for 3 years experience - Click here
- Core java interview questions and answers for 3-5 years exp - Click here
- Core java interview questions and Answers for 5 - 7 Years exp - Click here
- Basic Java Interview Questions and Answers - Click here
- Java interview questions and answers on oops - Click here
- Java interview questions and answers on Strings - Click here
- Java interview questions on exception handling - Click here
- Interview questions on multithreading in java for experienced - Click here
- Interview questions on serialization in java for experienced - Click here
- Interview questions on inner class in java for experienced - Click here
- Interview questions on Collections in java for experienced - Click here
Upcoming questions in next post:
47. Can we declare constructor,methods and fields inside ENUM definition.
48. When the constructor will be executed once you declare the constructor inside enum.
49. What is the difference between enum, Enum and Enumeration.
50. What is Assertion. What is the role of Assertion in java development.
51. Can we declare class inside interface.
52. Can we declare interface inside a class.
53. Can we declare class inside a class.
54. Can we declare interface inside a interface.
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Thank you techies for visiting this blog. I hope you enjoyed this blog and got more technical knowledge. I have tried to cover all types of questions and provided examples tested on eclipse as much as I can. Guys, please don’t just mug up the questions and answers. Try to clear your concepts with examples. Try to write a code on eclipse once you read the concepts. It will help you to memorize the concepts for a very long time. Simultaneously you will be prepared for interview programs as well. It will help you to survive in the IT sector for a long time. It may be easy to crack an interview but it's really tough to survive in the IT industry with inadequate knowledge and skills. I have collected all the questions from actual interviews attended by my friends, colleagues, college mate and classmate. I have covered frequently asked questions as well as challenging questions. I have included many programs to understand the concept thoroughly. I will try to explain the concept with the help of a real-time program in eclipse. You can share more questions which are not covered in this blog or post. Always welcome your suggestions and queries. I will definitely try to resolve it. Please comment your queries and new set of questions under the comment sections. I will create a new post for those questions.
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