InstanceOfJava

Bitwise operators in java with example

Posted by: Instanceofjava Posted date: 11:57 AM / comment : 0 Core java Interview Questions

Bitwise operators in java performs operation on bits
Bitwise operators performs bit by bit operations
Bit-wise operators operates on individual bits of operands.

Bit wise Operators in Java:

~ : Bit wise unary not
& : Bit wise And
| : Bit wise OR
^ : Bit wise Exclusive OR

1.Bit wise Unary Not ~:

Bit wise Unary not Inverts the bits.
Lets see a java program on bit wise unary not

Java Example program on bit wise unary not operator ~:

package operatorsinjava;
public class BitwiseUnaryNotDemo {
/**
* @www.instanceofjava.com
*/
public static void main(String[] args) {
int x=2;
System.out.println(~x);
int y= 3;
System.out.println(~y);
int z= 4;
System.out.println(~z);
}
}

Output:

-3
-4
-5

2. Bitwise AND operator:

Bit wise And returns 1 if both operands position values are 1 otherwise 0.
Bitwise operation on two numbers
1 & 2
001
010
-----
000 =0
-----
2 & 3
010
011
-----
010 =2
-----

Java Example program on bitwise AND operator &:

package operatorsinjava;
public class BitwiseAndDemo {
/**
* @www.instanceofjava.com
*/
public static void main(String[] args) {
int x=1;
int y=2;
System.out.println(x&y);
int i=2;
int j=3;
System.out.println(i&j);
System.out.println(4&5);
}
}

Output:

3.Bitwise OR operator in Java | :

Bit wise OR returns 1 if any one operands position values are 1 or both 1 s. otherwise 0.
1 |2
001
010
-----
011 =3
-----
2 | 3
010
011
-----
011 =3
-----

Java Example program on bitwise OR operator |:

package operatorsinjava;
public class BitwiseORDemo {
/**
* @www.instanceofjava.com
*/
public static void main(String[] args) {
int x=1;
int y=2;
System.out.println(x|y);
int i=2;
int j=3;
System.out.println(i|j);
System.out.println(4|5);
}
}

Output:

4.Bit wise Exclusive OR operator in java ^:

Bit wise XOR operator returns 1 if any of the operands bits position 1
Java XOR operator returns 0 if both operands position is 1.
Lest see java Xor on 1 ^ 2
1 ^ 2
001
010
-----
011 =3
-----
Lest see java xor operation on 2 ^3
2 ^ 3
010
011
-----
001 =1
-----

Java Example program on bitwise OR operator |:

package operatorsinjava;
public class BitwiseXORDemo {
/**
* @www.instanceofjava.com
*/
public static void main(String[] args) {
int x=1;
int y=2;
System.out.println(x^y);
int i=2;
int j=3;
System.out.println(i^j);
System.out.println(4^5);
}
}

Output:

Ternary operator in java

Posted by: Instanceofjava Posted date: 2:29 PM / comment : 0 Core java Interview Questions

Ternary operator also known as conditional operator in java.
Ternary operator used to evaluate boolean expression and it consists of three operands.

In Java, the ternary operator is a shorthand way to write an if-else statement. The operator has the following general form:

(condition) ? expression1 : expression2

The condition is a Boolean expression that is evaluated to either true or false. If the condition is true, the operator returns the value of expression1, and if the condition is false, it returns the value of expression2.

Here's an example of how you might use the ternary operator in a Java program:

int x = 5;

int y = 10;

int min = (x < y) ? x : y;

System.out.println(min); // Output: 5

In the above example, the ternary operator compares the values of x and y, and assigns the value of x to the variable min if x is less than y, and assigns the value of y to min otherwise. This can be interpreted as (x<y) ? min=x : min=y .

It's also possible to use ternary operator for more complex use cases like below:

String result = condition ? "value if true" : anotherVar == null ? "null value" : anotherVar;

It's worth noting that, although ternary operator is a shorthand way to write an if-else statement, it can make code harder to read when the expressions are too long or the conditions are too complex. In such cases, it's often better to use an if-else statement instead.

Ternary operator in java syntax:

variable x = (expression) ? value if true : value if false

Value of x will be decided based on the condition. if condition is true then it assigns first value to the variable
If Expression is false then it assigns second value to the variable.

Java simple example program on ternary operator / conditional operator in java

package operatorsinjava;
public class TernaryOperator {
/**
* @ www.instanceofjava.com
*
*/
public static void main(String[] args) {
// checking condition 2>3 and if true assign 3 else 3
int x= (2>3)?3:2;
System.out.println(x);
// checking condition 5<4 if true assign 4 else 3
int y= (5<4)?4:3;
System.out.println(y);
}
}

Output:

Ternary operator in java for boolean:

Java simple example program on ternary operator / conditional operator for boolean

package operatorsinjava;
public class TernaryOperator {
/**
* @ www.instanceofjava.com
*
*/
public static void main(String[] args) {
boolean x= true ? true: false;
System.out.println(x);
boolean y= false ? true : false;
System.out.println(y);
boolean z= false ? false : true;
System.out.println(z);
}
}

Output:

true
false
true

Ternary operator in java for Strings:

Java simple example program on ternary operator / conditional operator for String

package operatorsinjava;
public class TernaryOperatorForStrings{
/**
* @ www.instanceofjava.com
*
*/
public static void main(String[] args) {
String str= "java".equals("java") ? "Java Questions" : "Java Programs";
System.out.println(str);
String str1= (1==3)? "its true" : "its false";
System.out.println(str1);
}
}

Output:

Java Questions
its false

Ternary operator in java for null;

Java simple example program on ternary operator / conditional operator for null check

package operatorsinjava;
public class TernaryOperatorForStrings{
/**
* @ www.instanceofjava.com
*
*/
public static void main(String[] args) {
String str= null;
String str1= (str==null) ? "its true" : "its false";
System.out.println(str1);
String str2= (str1!=null) ? "its true" : "its false";
System.out.println(str2);
}
}

Output:

its true
its true

Top 20 Java Exception handling interview questions and answers

Posted by: Instanceofjava Posted date: 12:11 PM / comment : 1 exception handling interview questions , java programming interview questions

1.What is an exception?

Exceptions are the objects representing the logical errors that occur at run time and makes JVM enters into the state of "ambiguity".
The objects which are automatically created by the JVM for representing these run time errors are known as Exceptions

2.What are the differences between exception and error.

An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch. Most such errors are abnormal conditions.
Difference between exception and error

3.How the exceptions are handled in java

Exceptions can be handled using try catch blocks.
The statements which are proven to generate exceptions need to keep in try block so that whenever is there any exception identified in try block that will be assigned to corresponding exception class object in catch block
More information about try catch finally

4.What is the super class for Exception and Error

Throwable.

public class Exception extends Throwable implements Serializable

public class Error extends Throwable implements Serializable

5.Exceptions are defined in which java package

java.lang.Exception

6.What is throw keyword in java?

Throw keyword is used to throw exception manually.
Whenever it is required to suspend the execution of the functionality based on the user defined logical error condition we will use this throw keyword to throw exception.
Throw keyword in java

7.Can we have try block without catch block

It is possible to have try block without catch block by using finally block
Java supports try with finally block
As we know finally block will always executes even there is an exception occurred in try block, Except System.exit() it will executes always.
Is it possible to write try block without catch block

8.Can we write multiple catch blocks under single try block?

Yes we can write multiple catch blocks under single try block.
Multiple catch blocks in java

exception handling interview questions and answers

9. What are unreachable blocks in java

The block of statements to which the control would never reach under any case can be called as unreachable blocks.
Unreachable blocks are not supported by java.
Unreachable blocks in java

unreachable block exception handling interview question

10.How to write user defined exception or custom exception in java

By extending Exception class we can define custom exceptions.
We need to write a constructor for passing message .
User defined exception in java

class CustomException extends Exception { } // this will create Checked Exception
class CustomException extends IOExcpetion { } // this will create Checked exception
class CustomException extends NullPonterExcpetion { } // this will create UnChecked
exception

11.What are the different ways to print exception message on console.

In Java there are three ways to find the details of the exception .
They are

Using an object of java.lang.Exception
Using public void printStackTrace() method
Using public String getMessage() method.

3 different ways to print exception message in java

12.What are the differences between final finally and finalize in java

Finally vs final vs finalize

13.Can we write return statement in try and catch blocks

Yes we can write return statement of the method in try block and catch block
We need to follow some rules to use it.Please check below link
Return statement in try and catch blocks

return statement in try catch block exception handling

14. Can we write return statement in finally block

Yes we can write return statement of the method in finally block
We need to follow some rules to use it.Please check below link
Return statement in finally block

return statement in finally exception handling interview

15. What are the differences between throw and throws

throw keyword used to throw user defined exceptions.(we can throw predefined exception too)
Using throws keyword we can explicitly provide the information about unhand-led exceptions of the method to the end user, Java compiler, JVM.
Throw vs throws

16.Can we change an exception of a method with throws clause from unchecked to checked while overriding it?

No. As mentioned above already
If super class method throws exceptions in sub class if you want to mention throws then use same class or its sub class exception.
So we can not change from unchecked to checked

17.What are the rules we need to follow in overriding if super class method throws exception ?

If sub class throws checked exception super class should throw same or super class exception of this.
If super class method throws checked or unchecked exceptions its not mandatory to put throws in sub class overridden method.
If super class method throws exceptions in sub class if you want to mention throws then use same class or its sub class exception.

18.What happens if we not follow above rules if super class method throws some exception.

Compile time error will come.

package MethodOverridingExamplePrograms;
public class Super{
public void add(){
System.out.println("Super class add method");
}
}

package MethodOverridingInterviewPrograms;
public class Sub extends Super{
void add() throws Exception{ //Compiler Error: Exception Exception is not compatible with
throws clause in Super.add()
System.out.println("Sub class add method");
}
}

package ExceptionHandlingInterviewPrograms;
public class Super{
public void add(){
System.out.println("Super class add method");
}
}

package ExceptionHandlingInterviewPrograms;
public class Sub extends Super{
void add() throws NullPointerException{ // this method throws unchecked exception so no
isuues
System.out.println("Sub class add method");
}
}

19. Is it possible to write multiple exceptions in single catch block

It is not possible prior to java 7.
new feature added in java 7.

package exceptionsFreshersandExperienced;
public class ExceptionhandlingInterviewQuestions{
/**
* @www.instanceofjava.com
**/
public static void main(String[] args) {
try {
// your code here
} catch (IOException | SQLException ex) {
System.out.println(e);
}
}
}

20. What is try with resource block

One more interesting feature of Java 7 is try with resource
In Java, if you use a resource like input or output streams or any database connection logic you always need to close it after using.
It also can throw exceptions so it has to be in a try block and catch block. The closing logic should be in finally block. This is a least the way until Java 7. This has several disadvantages:
1. You'd have to check if your ressource is null before closing it
2. The closing itself can throw exceptions so your finally had to contain another try -catch
3. Programmers tend to forget to close their resources

The solution given by using try with resource statement.

try(resource-specification)
{
//use the resource
}catch(Exception e)
{
//code
}

Top 20 Java Exception handling interview questions and answers for freshers and experienced

3 different ways to print exception message in java

Posted by: Instanceofjava Posted date: 3:23 PM / comment : 0 exception handling interview questions

In Java there are three ways to find the details of the exception .
They are

Using an object of java.lang.Exception
Using public void printStackTrace() method
Using public String getMessage() method.

1.Using an object of java.lang.Exception

An object of Exception class prints the name of the exception and nature of the exception.

Write a Java program get detailed message details using exception class object

package exceptions;
public class ExceptionDetails {
/**
* @www.instanceofjava.com
**/
public static void main(String[] args) {
try {
int x=1/0;
} catch (Exception e) {
System.out.println(e);
}
}
}

Output:

java.lang.ArithmeticException: / by zero

2.Using public void printStackTrace() method

This is the method which is defined in java.lang.Throwable class and it is inherited into java.lang.Error class and java.lang.Exception class
This method will display the name of the exception and nature of the message and line number where exception has occurred.

Write a simple java example program to print exception message to console using printStacktrace() method

package exceptions;
public class ExceptionDetails {
/**
* @www.instanceofjava.com
*/
public static void main(String[] args) {
try {
int a[]= new int[1];
a[1]=12
} catch (Exception e) {
e.printStackTrace();
}
}
}

Output:

java.lang.ArrayIndexOutOfBoundsException: 1
at exceptions.ExceptionDetails.main(ExceptionDetails.java:13)

3.Using public String getMessage() method

This is also a method which is defined in java.lang.Throwable class and it is inherited in to both java.lanf.Error and java.lang.Exception classes.
This method will display the only exception message

Write a Java program print exception message using getMessage() method.

package exceptions;
public class ExceptionDetails {
/**
* @www.instanceofjava.com
*/
public static void main(String[] args) {
try {
int x=1/0;
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
}

Output:

/ by zero

throw keyword in java with example

Posted by: Instanceofjava Posted date: 2:36 PM / comment : 0 exception handling interview questions

Throw keyword in java

Throw keyword is used to throw exception manually.
Whenever it is required to suspend the execution of the functionality based on the user defined logical error condition we will use this throw keyword to throw exception.
So we need to handle these exceptions also using try catch blocks.

Java simple example Program to explain use of throw keyword in java

package exceptions;
public class ThrowKeyword {
public static void main(String[] args) {
try {
throw new ArithmeticException();
} catch (Exception e) {
System.out.println(e);
e.printStackTrace();
}
}
}

Output:

java.lang.ArithmeticException
java.lang.ArithmeticException
at exceptions.ThrowKeyword.main(ThrowKeyword.java:11)

Rules to use "throw" keyword in java

throw keyword must follow Throwable type of object.
It must be used only in method logic.
Since it is a transfer statement , we can not place statements after throw statement. It leads to compile time error Unreachable code

We can throw user defined exception using throw keyword.

//Custom exception
package com.instanceofjavaforus;
public class InvalidAgeException extends Exception {
InvaidAgeException(String msg){
super(msg);
}
}

package com.exceptions;
public class ThrowDemo {
public boolean isValidForVote(int age){
try{
if(age<18){
throw new InvalidAgeException ("Invalid age for voting");
}
}catch(Exception e){
System.out.println(e);
}
return false;
}
public static void main(String agrs[]){
ThrowDemo obj= new ThrowDemo();
obj.isValidForVote(17);
}
}

Output:

exceptions.InvalidAgeException: Invalid age for voting

We can throw predefined exceptions using throw keyword

package com.instanceofjava;
public class ThrowKeyword{
public void method(){
try{
throw new NullPointerException("Invalid age for voting");
}
}catch(Exception e){
System.out.println(e);
}
}
public static void main(String agrs[]){
ThrowKeyword obj= new ThrowKeyword();
obj.method();
}
}

Output:

java.lang.NullPointerException: Invalid age for voting

Multiple catch blocks in java example

Posted by: Instanceofjava Posted date: 12:11 PM / comment : 1 exception handling interview questions

Is there any chance of getting multiple exception?

Lets see a java example programs which can raise multiple exceptions.

package exceptions;
public class MultipleCatchBlocks {
/**
* @www.instanceofjava.com
*/
public static void main(String[] args) {
int x=10;
int y=0;
try{
int i=x/y;
int a[]=new int[2];
a[3]=12;
} catch(ArithmeticException e){
e.printStackTrace();
}
}
}

Output:

java.lang.ArithmeticException: / by zero
at exceptions.MultipleCatchBlocks.main(MultipleCatchBlocks.java:15)

Lets see second case:

In the 1st program there is a chance of getting two types of exceptions and we kept only one catch block with ArithmeticException e .
But there will be chance of getting ArrayIndexOutOfBoundsException too.
So we need to keep multiple catch blocks in order to handle all those exceptions
Or else we can keep single catch block with super class Exception class object.

Multiple catch blocks for single try block:

One try can have multiple catch blocks
Every try should and must be associated with at least one catch block.( try without catch)
Whenever an exception object is identified in try block and if there are multiple catch blocks then the priority for the catch block would be given based on order in which catch blocks are have been defined.
Highest priority would be always given to first catch block . If the first catch block can not handle the identified exception object then it considers the immediate next catch block.

Disadvantages of multiple catch blocks:

We have to know the names of every corresponding exception class names.
We have to understand which statement is generating which exception class object.

Solution:

Define a single catch block so that it should be able to handle any kind of exceptions identified in the try block.
Exception class is the super class for all the exception classes.
To the reference of super class object we can assign any sub class object.

Subscribe to: Posts ( Atom )