Part 4
Core java interview questions and answers for 3-5 years experience covered in this post:
Can you identify which try, catch and finally block combination is valid?
-
Following are the combinations.
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1. try {
}catch() {
} try { }catch() {
}
2. try { }catch() {
} try { }finally {
}
3. try { }
4. try { }finally { }catch() { }
1 and 2 are valid.
3 and 4 are invalid. |
How can you prevent particular variable to be serialized?
- Transient keyword can be used to prevent a particular variable to be
serialized.
- You can declare the variable as static. Static variables are not considered
for serialization.
- Please refer to the below example.
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package simplifiedjava.crackedInterview; import java.io.Serializable; public class Student implements Serializable {
private static final long serialVersionUID
= 1L;
private int id;
private transient
String name;
private
String dept;
public
Student(int id, String name, String dept) {
super();
this.id = id;
this.name = name;
this.dept = dept;
}
public int
getId() {
return id;
}
public void
setId(int id) {
this.id = id;
}
public
String getName() {
return name;
}
public void
setName(String name) {
this.name = name;
}
public
String getdept() {
return dept;
}
public void
setdept(String dept) {
this.dept = dept;
} } package simplifiedjava.crackedInterview;
import
java.io.File;
import
java.io.FileInputStream;
import
java.io.FileOutputStream;
import
java.io.IOException;
import
java.io.ObjectInputStream; import java.io.ObjectOutputStream; public class SerializationDemo { public static void main(String[] args) throws IOException, ClassNotFoundException { Student s1 = new Student(100,"Yogesh","IT");
File file1 = new
File("stud1.ser");
FileOutputStream fos = new
FileOutputStream(file1);
ObjectOutputStream oos = new
ObjectOutputStream(fos);
oos.writeObject(s1);
File file2 = new
File("stud1.ser");
FileInputStream fis = new
FileInputStream(file2);
ObjectInputStream ois = new
ObjectInputStream(fis);
Student s2
= (Student) ois.readObject();
System.out.println("Student ID :" + s2.getId());
System.out.println("Student Name :"+ s2.getName());
System.out.println("Student Dept :"+ s2.getdept());
}
}
Output:
Student ID :100
Student Name :null – This is not considered for
serialization.
Student Dept :IT
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What is static nested class?
- We can declare an inner class with a static modifier such types of inner
classes are called a static nested class.
- In the case of regular inner class without the existing outer class object
there is no chance of existing inner class object i.e. inner class object is
strongly associated with an outer class object.
- In the case of static nested classes without the existing outer class
object there may be a chance of existing inner class object. Hence, Static
nested class object is not strongly associated with an outer class
object.
- Please refer to the below example.
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package simplifiedjava.crackedInterview; public class StaticNestedClassDemo {
public static void
main(String[] args) {
Nested n = new
Nested();
n.m1(); }
static class
Nested{
public void
m1() {
System.out.println("Nested Class.");
}
}
} |
What is the purpose of Collections Utility class? What are the utility methods are available in Collections Class?
- Collections is a utility class for the collection
framework.
- Collections utility class has some methods which are as
follows.
1. addAll()
2. binarySearch()
3. checkedCollection()
4. copy()
5. fill()
6. min()
7. max()
8. replaceAll()
9. reverse()
10. shuffle()
11. synchronizedCollection()
12. unmodifiableCollection()
What is the difference between TreeMap and SortedMap?
|
|
TreeMap |
SortedMap |
|
1. |
TreeMap is a concrete class. |
SortedMap is an interface. |
What is ConcurrentModificationException?
- When one thread is performing a read operation other threads are not
allowed to perform any operation on the same object still you are attempting
the same then it will throw ConcurrentModificationException.
- Please refer to the below example.
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package simplifiedjava.crackedInterview;
import
java.util.HashMap;
import
java.util.Iterator; import java.util.Map; public class ConcurrentModificationExceptionDemo {
public static void
main(String[] args) {
HashMap<Integer,String> m = new
HashMap<Integer,String>();
m.put(101,"Shweta");
m.put(102,"Shruti");
Iterator itr = m.entrySet().iterator();
while(itr.hasNext()) {
m.put(103, "Anjali");
Map.Entry<Integer, String> pair
= (Map.Entry<Integer, String>)itr.next();
System.out.println("Key = "+ pair.getKey()+ "\t Value = "+ pair.getValue());
}
}
}
Output:
Exception in thread "main" java.util.ConcurrentModificationException
at
java.util.HashMap$HashIterator.nextNode(Unknown Source)
at
java.util.HashMap$EntryIterator.next(Unknown Source)
at
java.util.HashMap$EntryIterator.next(Unknown Source)
at
simplifiedjava.crackedInterview.ConcurrentModificationExceptionDemo.main(ConcurrentModificationExceptionDemo.java:17)
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What is type interface?
- Type safety means that the compiler will validate types while compiling,
and throw an error if you try to assign the wrong type to a variable.
Please identify valid lambda expression?
-
() -> System.out.println("Hello");
-
(s) -> System.out.println("Java");
-
(a,10) -> {System.out.println(a);
System.out.println(10);}
-
(a,b) -> System.out.println(a+b);
-
s -> {System.out.println(s);}
-
(int a, int b) -> {System.out.println(a+b);}
-
s -> s.length();
-
(s) -> {s.length();}
|
Expression |
Valid / Invalid |
|
() -> System.out.println("Hello"); |
Valid |
|
(s)-> System.out.println("Java"); |
Valid |
|
(a,10) -> {System.out.println(a);
System.out.println(10);} |
Valid |
|
(a,b) -> System.out.println(a+b); |
Valid |
|
s -> {System.out.println(s);} |
Valid |
|
(int a, int b) -> {System.out.println(a+b);} |
Valid |
|
s -> s.length(); |
Valid |
|
(s) -> {s.length();} |
Valid |
How will you identify particular method is default method?
- All default methods must be declared inside the interface. You cannot
declare the default method inside the class.
- All default methods are declared with the default
keyword.
What is the difference between Function
and Bi-Function?
|
|
Function |
Bi-Function |
|
1. |
The Function accepts two parameters. |
Bi-Function accepts three parameters. |
|
2. |
@FunctionalInterface
public interface Function<T, U> {
} |
@FunctionalInterface
public interface BiFunction<T,U,R>{
} |
- 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
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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.
My total experience is 10. Initially I had worked on some
support projects and then I moved to java projects. I had
worked with many multi-national companies like R-Systems,
Tata Consultancy Services, Cybage
Softwares. Fortunately, TCS and Cybage has
given me an opportunity to take interviews for experienced
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1 Comments
Excellent Compilation for java interview.
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