InstanceOfJava

Differences between Default constructor and no argument constructor in java

Posted by: Instanceofjava Posted date: 3:49 PM / comment : 0 Core java Interview Questions

Differences between default constructor and no argument constructor

Default Constructor in java:

When we write a class without any constructor then at compilation time java compiler creates a default constructor in our class.
The accessibility modifier of the default constructor is same as accessibility modifier of class.
The allowed accessibility modifier are public and default.
Default constructor added by java compiler this constructor does not have anything except super(); call.

package constructor;
public class A {
}

package constructor;
public class A {
A(){
super();
}
}

If our class have any constructor then java compiler does not create default constructor

No-argument Constructor in java:

As a developer we can create our own constructor with no arguments is known as no-argument constructor.
It can have all four accessibility modifiers as it is defined by developer.
So allowed accessibility modifiers are public, private, protected and default
It can have logic including super call.

package constructor;
public class A {
A(){
super();
System.out.println("no -argument constructor");
}
}

The common point between default and no-argument constructor
Both does not have any arguments.
And one more point we need to remember that in no-argument constructor also by default first statement will be super() call which is added by java compiler if it does not have.

Remove specified element from Java LinkedHashSet example

Posted by: Instanceofjava Posted date: 3:10 PM / comment : 0 java Collections interview Questions , java programs for freshers , LinkedHashSet

1.Basic java example program to remove particular element in linkedhashset

boolean remove(Object o) This method used to remove specified element from Linkedhashset.

package com.removeelementLinkedhashset;
import java.util.LinkedHashSet;
import java.util.Iterator;
public class LinkedHashsetExample{
public static void main(String[] args) {
LinkedHashSet<String> linkedhashset = new LinkedHashSet<>();
linkedhashset.add("Java Interview Questions");
linkedhashset.add("Java interview program");
linkedhashset.add("Concept and example program");
linkedhashset.add("Concept and interview questions");
linkedhashset.add("Java Quiz");
System.out.println("LinkedHashSet before removal : " + linkedhashset);
boolean blnRemoved = linkedhashset.remove("Java Quiz");
System.out.println("Was Java Quiz removed from LinkedHashSet ? " + blnRemoved);
System.out.println("LinkedHashSet after removal : ");
Iterator it=linkedhashset.iterator();
while(it.hasNext()){
System.out.println(it.next());
}
}
}

Output:

LinkedHashSet before removal : [Java Interview Questions, Java interview program, Concept
and example program, Concept and interview questions, Java Quiz]
Was Java Quiz removed from LinkedHashSet ? true
Java Interview Questions
Java interview program
Concept and example program
Concept and interview questions

Check if a particular element exists in Java LinkedHashSet Example

Posted by: Instanceofjava Posted date: 2:55 PM / comment : 0 java Collections interview Questions , LinkedHashSet

1.Basic java example program to check particular element is exists in linkedhashset

boolean contains(Object o) This method Returns true if this set contains the specified element

package com.checkelementhashset;
import java.util.LinkedHashSet;
import java.util.Iterator;
public class LinkedHashsetExample{
public static void main(String[] args) {
LinkedHashSet<String> linkedhashset = new LinkedHashSet<>();
linkedhashset.add("Java Interview Questions");
linkedhashset.add("Java interview program");
linkedhashset.add("Concept and example program");
linkedhashset.add("Concept and interview questions");
linkedhashset.add("Java Quiz");
/*
To check whether a particular value exists in LinkedHashSet we need to use
boolean contains(Object value) method of HashSet class.
this method returns true if the LinkedHashSet contains the value, otherwise returns false.
*/
boolean isExists = linkedhashset.contains("Java Quiz");
System.out.println("Java Quiz exists in LinkedHashSet? : " + isExists);
Iterator it=linkedhashset.iterator();
while(it.hasNext()){
System.out.println(it.next());
}
}
}

Output:

Java Quiz exists in LinkedHashSet ? : true
Java Interview Questions
Java interview program
Concept and example program
Concept and interview questions
Java Quiz

Return statement in finally block in java

Posted by: Instanceofjava Posted date: 1:02 PM / comment : 0 exception handling interview questions , finally with return

Can we write return statement in finally block

Finally block will executes always excepts system.exit().
So if we are returning some value in finally means it will be returned always
Finally will executed so method always returns finally return value and no need of keeping return value at end of the method.
And in finally after return if we keep some statement those statement will be treated as dead code.

i)Return statement in finally block

package com.exceptionhandlingiinterviewquestions;
public class TryCatchReturn{
int calc(){
try {
} catch (Exception e) {
}
finally(){
return 1;
}
System.out.println("End of the method"); // Error : Unreachable code
}
public static void main(String[] args) {
TryCatchReturn obj = new TryCatchReturn();
}
}

ii) return statement in finally

package com.exceptionhandlingiinterviewquestions;
public class TryCatchReturn{
int calc(){
try {
} catch (Exception e) {
}
finally(){
return 1;
System.out.println("End of the method"); // Error : Unreachable code
}
}
public static void main(String[] args) {
TryCatchReturn obj = new TryCatchReturn();
}
}

iii) return statement in try catch and finally blocks

package com.exceptionhandlingiinterviewquestions;
public class TryCatchReturn{
int calc(){
try {
return 10;
} catch (Exception e) {
return 20;
}
finally(){
return 30;
}
}
public static void main(String[] args) {
TryCatchReturn obj = new TryCatchReturn();
System.out.println(obj.calc())
}
}

Output:

Remove specified element from Java HashSet example

Posted by: Instanceofjava Posted date: 12:23 PM / comment : 0 hashset , java Collections interview Questions

1.Basic java example program to remove element hashset

boolean remove(Object o) . This method is used to remove element from hashset if it is present it returns true.

package com.getSizehashset;
import java.util.HashSet;
import java.util.Iterator;
public class HashsetExample{
public static void main(String[] args) {
//create object of HashSet
HashSet<Integer> hashSet = new HashSet();
//add elements to HashSet object
hashSet.add(1);
hashSet.add(2);
hashSet.add(3);
hashSet.add(4);
hashSet.add(5);
hashSet.add(6);
hashSet.add(7);
hashSet.add(8);
System.out.println("Size of HashSet after addition : " + hashSet.size());
System.out.println("Hashset contains");
Iterator it=hashSet.iterator();
while(it.hasNext()){
System.out.println(it.next());
}
boolean isRemoved = hashSet.remove(6);
System.out.println("Was 6 removed from HashSet ? " + isRemoved );
System.out.println("HashSet after removal : " + hashSet);
}
}

Output:

Size of HashSet after addition
8
hashset contains
1
2
3
4
5
6
7
8
Was 6 removed from HashSet ?true
HashSet after removal : [1, 2, 3, 4,5,7,8]

Get Size of Java HashSet Example

Posted by: Instanceofjava Posted date: 12:14 PM / comment : 0 hashset , java Collections interview Questions

1.Basic java example program to get size of hashset

int size() This method is used get get size of hashset

package com.getSizehashset;
import java.util.HashSet;
import java.util.Iterator;
public class HashsetExample{
public static void main(String[] args) {
//create object of HashSet
HashSet<Integer> hashSet = new HashSet();
//add elements to HashSet object
hashSet.add(1);
hashSet.add(2);
hashSet.add(3);
hashSet.add(4);
hashSet.add(5);
hashSet.add(6);
hashSet.add(7);
hashSet.add(8);
System.out.println("Size of HashSet after addition : " + hashSet.size());
System.out.println("Hashset contains");
Iterator it=hashSet.iterator();
while(it.hasNext()){
System.out.println(it.next());
}
}
}

Output:

Size of HashSet after addition
8
hashset contains
1
2
3
4
5
6
7
8

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