Types of Exceptions and Exception Handling in Java

Types of Exception

 Checked Exception
 Unchecked Exception

Common scenarios of Exception Handling
 ArithmeticException

int a=50/0;

 NullPointerException

String s=null;
System.out.println(s.length());

Common scenarios of Exception Handling
 NumberFormatException

String s=“abc”;
int i=Integer.parseInt(s);

 ArrayIndexOutOfBoundsException

int a[]= new int[5];
a[10]=50;

Keywords used Exception Handling
 try
 catch
 finally
 throw
 throws

try
class sample
{
public static void main(String args[])
{
int data=50/0;
System.out.println(“I love india”);
}
}

try
class sample{
public static void main(String args[]){
try{
int data=50/0;
}
catch(ArithmeticException e)
{
System.out.println(e);
}
}
}

Multiple catch
class sample{
try{
int a[]=new int[5];
int a[5]=30/0; }
catch(ArithmeticException e){s.o.p(“task 1”);}
catch(ArrayIndexOutOfBoundsExceptin e){s.o.p(“task 2”);}
catch(Exception e){s.o.p(“task completed”);}
}
}

Multiple catch
class sample{
try{
int a[]=new int[5];
int a[5]=30/0; }
catch(Exception e){s.o.p(“task completed”);}
catch(ArithmeticException e){s.o.p(“task 1”);}
catch(ArrayIndexOutOfBoundsExceptin e){s.o.p(“task 2”);}
}
}

Nested try
class sample{
try{
try{
s.o.p(“divide”);
int a=40/0;
}catch(ArithmeticExceptin e){s.o.p(e);}
try{
int a[]=new int[5];
int a[5]=4;
}catch(ArrayIndexOutOfBoundsExceptin e){
s.o.p(e);}
s.o.p(“other statements”);
}catch(Exception e){s.o.p(“exception handled”);}
s.o.p(“normal flow”);
}
}

finally
 Exception doesn’t occur
class sample{
try{
int data=25/5;
s.o.p(data);}
catch(NullPointerException e){s.o.p(e);}
finally{s.o.p(“finally block is always excuted”);}
s.o.p(“I love india”);
}
}

finally
 Exception occurred but not handled
class sample{
try{
int data=25/0;
s.o.p(data);}
catch(NullPointerException e){s.o.p(e);}
}
}

finally
 Exception occurred but handled
class sample{
try{
int data=25/0;
s.o.p(data);}
catch(ArithmeticException e){s.o.p(e);}
}
}

throw
class sample{
static void validate(int age){
if(age<18)
throw new ArithmeticException(“not valid”);
else
System.out.println(“welcome to vote”);
}
pulic static void main(String args[]){
validate(13);
}
}

Exception Propagation
class sample{
void m(){
int data=50/0; }
void n(){
m(); }
void p(){
try{
n();
}catch(Exception e){s.o.p(“Exception handled”);}
}
sample obj=new sample();
obj.p();
}
}

Exception Propagation
class sample{
void m(){
throw new java.io.IOException(“device error”); }
void n(){
m(); }
void p(){
try{
n();
}
obj.p();
}
}

throws
 Checked exception can be propagated by throws keyword
import java.io.IOException;
class sample{
void m() throws IOException {
throw new IOException(“device error”); }
void n() throws IOException{
m(); }
void p(){
try{
n();
}
obj.p();
}
}

Handling the exception if exception occurs in the
method which declares an exception
import java.io.*;
class M{
void method() throws IOException {
throw new IOException(“device error”);}
}
class Test{
publi static void main(String args[]){
try{
M m=new M();
m.method();
}catch(Exceptionn e){s.o.p(“exception handled”);}
System.out.println(“I love india”);}
}

Declaring the exception if exception doesn’t
occur in the method which declares an exception
import java.io.*;
class M{
System.out.println(“device operation perform”);}
}
class Test{
publi static void main(String args[]) throws
IOException{
M m=new M();
m.method();
}
}

Declaring the exception if exception occurs in the
method which declares an exception
import java.io.*;
class M{
throw new IOException(“device error”);}
}
class Test{
publi static void main(String args[]) throws
IOException{
M m=new M();
m.method();
System.out.println(“I love india”);}
}
}

Exception Handling with Method
Overriding

 Super class method doesn’t declare an exception
 Subclass overridden method can’t declare the checked
exception
import java.io.*;
class Parent{
void msg(){s.o.p(“parent”);}
}
class Child extends Parent{
void msg() throws IOException{
System.out.println(“child”);
}
Parent p=new Child();
p.msg();
}
}

 Super class method doesn’t declare an exception
 Subclass overridden method can declare the unchecked
exception
import java.io.*;
class Parent{
void msg(){s.o.p(“parent”);}
}
void msg() throws ArithmeticException{
System.out.println(“child”);
}
p.msg();
}
}

Super class method declares an exception
 Subclass overridden method declares parent exception
import java.io.*;
class Parent{
void msg()throws ArithmeticException{s.o.p(“parent”);}
}
void msg() throws Exception{System.out.println(“child”); }
try{
p.msg();
}catch(Exception e){}
}
}

 Subclass overridden method declares same exception
import java.io.*;
class Parent{
void msg()throws Exception{s.o.p(“parent”);}
}
void msg() throws Exception{System.out.println(“child”); }
try{
p.msg();
}
}

 Subclass overridden method declares subclass exception
import java.io.*;
class Parent{
}
void msg() throws ArithmeticException{s.o.p(“child”); }
try{
p.msg();
}
}

 Subclass overridden method declares no exception
import java.io.*;
class Parent{
}
void msg() {s.o.p(“child”); }
try{
p.msg();
}
}

Custom Exception
class sample{
static void validate(int age) throws InvalidAgeException{
if(age<18)
throw new InvalidAgeException(“not valid”);
else
System.out.println(“welcome to vote”);
}
try{
validate(13);
}catch(Exception m){s.o.p(“Exception occured” +m);}
}
}

Types of Exceptions and Exception Handling in Java

Types of Exceptions and Exception Handling in Java

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Types of Exceptions and Exception Handling in Java