Core java interview questions and answers for 3-5 years experience

 Part 7

Core java interview questions and answers for 3-5 years experience covered in this post:

    Does the finally block get executed if the try or catch block has a return statement? How the control flows in this situation?

-  Yes. finally{} block will be executed even though you have a return statement in either try block or catch block.

-    finally{} block will be executed prior to the return statement execution.

-   finally{} block will not be executed only in one condition. Once you invoke System.exit(0) your JVM will be crashed and the finally{} block will not be executed.

  

    What is the difference between Synchronization Method and Synchronized Block?

	Synchronization Method	Synchronized Block
1.	A method declared with a Synchronized keyword is called Synchronized Method.	Inside a method, if a chunk of code declared inside block with Synchronized keyword is called a Synchronized block.
2.	Performance is low as compared to Block.	Performance is high as compared to the method.

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    If your child class is Serializable and parent class is not and child class is inheriting some properties of parent class, in that case can you serialize child class?

-      Yes, In that case, we can serialize the child class object.

-     But while serialization, JVM will ignore the original value of parent class instance variables and save the default value to file.

-    At the time of de-serialization, if any non-serializable superclass is present then JVM will execute instance control flow in the superclass. To execute instance control flow in a class, JVM will always invoke the default(no-arg) constructor of that class. So every non-serializable superclass must necessarily contain a default constructor, otherwise, we will get InvalidClassException.

-       Please refer to the below example.

package simplifiedjava.crackedInterview;  public class Parent {        public int i;            public Parent() {             System.out.println("Parent Class no-arg constructor called.");       }            public Parent(int i) {             this.i = i;       }                            public void check(){             System.out.println("Parent Class check() method");                }     }  package simplifiedjava.crackedInterview; import java.io.Serializable;  public class Child extends Parent implements Serializable{            int j;            public Child() {                  }       public Child(int i,int j) {             super(i);             this.j = j;       }            public void check(){             System.out.println("Addition in Child Class "+ (i + j));                }     }  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 SerializationInHeritanceDemo {        public static void main(String[] args) throws IOException, ClassNotFoundException {                        Child c1 = new Child(10,20);             System.out.println(c1.i +" and "+ c1.j);                                FileOutputStream fos = new FileOutputStream(new File("abc.ser"));             ObjectOutputStream oos = new ObjectOutputStream(fos);             oos.writeObject(c1);                         FileInputStream fis = new FileInputStream("abc.ser");             ObjectInputStream ois = new ObjectInputStream(fis);             Child c2 =(Child) ois.readObject();             System.out.println(c2.i +" and "+ c2.j);       } } Output: Values Before Serialization : 10 and 20 Parent Class no-arg constructor called. Values After Deserialization : 0 and 20

    Can we declare constructor inside anonymous inner class?

-          No, we cannot declare a constructor inside an anonymous inner class.

-      Anonymous inner class doesn’t have any name and the constructor name should be the same as the class name. If the class name does not exist then how can we create a constructor?

    What is SortedSet? What is the purpose of SortedSet?

-          If we want to represent a group of individual objects according to some sorting order without duplicate then we should go for SortedSet.

-          SortedSet interface is a child interface of the Set interface.

-          Null is not allowed in SortedSet implementation.

-          All elements inserted into a sorted set must implement the Comparable interface (or be accepted by the specified comparator).

-          Please refer to the below example. 

package simplifiedjava.crackedInterview;  import java.util.SortedSet; import java.util.TreeSet;  public class SortedSetDemo {        public static void main(String[] args) {             SortedSet<Integer> set = new TreeSet<Integer>();             set.add(50);             set.add(10);             set.add(30);             set.add(20);             set.add(40);                        System.out.println(set);       } } Output: [10, 20, 30, 40, 50]

    What do you mean by Concurrency Level?

-  Concurrency divided map objects into 16 parts that smaller parts are known as Concurrency level.

    What is Generic Type Parameter?

-          Type parameter is an identifier that specifies a generic type name.

-          Type parameter is also known as the Type variable.

-          Type parameter can be used to declare the return type.

-          Please refer to the syntax.

class ArrayList<T>{       add(T t);       T get(int index); }  class ArrayList<String>{       add(String s);       String get(int index); }

 -          Please refer to the below example.

package simplifiedjava.crackedInterview; public class GenericTemplate<T> {        T obj;            public GenericTemplate(T obj) {             this.obj = obj;       }           public T getobj() {             return obj;       }       public void show() {             System.out.println("Type of Object "+ obj.getClass().getName());       } }  package simplifiedjava.crackedInterview;  public class GenericDemo {        public static void main(String[] args) {             GenericTemplate<String> str = new GenericTemplate<String>("Yogesh");             str.show();             System.out.println(str.getobj());                        GenericTemplate<Integer> numbers = new GenericTemplate<Integer>(100);             numbers.show();             System.out.println(numbers.getobj());                        GenericTemplate<Double> dblNum = new GenericTemplate<Double>(25.50);             dblNum.show();             System.out.println(dblNum.getobj());       } }  Output: Type of Object java.lang.String Yogesh Type of Object java.lang.Integer 100 Type of Object java.lang.Double 25.5

    What is the return type of apply method in Consumer functional interface?

-          The return type of accept method is void.

-          Accept() method only consumes the input and process it.

    What is the difference between Abstract class and Interface with Default methods?

	Abstract class	Interface with Default methods
1.	An abstract class can be declared with an abstract keyword.	Interface with default method declared with interface keyword and default keyword for method.
2.	An abstract class can have a constructor.	An interface cannot have a constructor. Doesn’t matter interface has a default method or not.
3.	An abstract class can have a static block or a non-static block.	Interface with the default method cannot have a static or non-static block.
4.	Abstract class can’t refer to lambda expression.	Interface with default methods refers to lambda expression.
5.	Inside the abstract class, we can override the objects class method.	We cannot override objects class method in interface with default methods.
6.	An abstract class can be declared protected members.	Interface with default methods cannot declare protected members.

    What is the abstract method defined in Function functional interface?

-          Function interface has defined apply() as an abstract method.

-          Please refer to the below example for syntax.

@FunctionalInterface public interface Function<T, R> {   R apply(T t); }

• 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:

71. What will happen If I directly override run method instead of start() method. 

72. What is the difference between Regular Inner Class and Static Inner Class.

73. How to remove the duplicates from list object without stream API.

74. Can we use ConcurrentHashMap in place of Hashtable?

75. What is the difference between ConcurrentHashMap and SynchronizedHashMap.

76. How will you identify lambda expression.

77. What will happen if I declared multiple abstract methods in one interface.

78. How will you invoke static methods from class.

79. What is Bi-Function functional interface.

80. Wap to implement Bi-Function interface.

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