Exception Dealing with in Java with Examples | 2023

Exception dealing with in java is likely one of the highly effective mechanisms to deal with runtime errors attributable to exceptions. Exception dealing with performs an vital position in software program growth. This text helps you perceive java exception, exception in java, java exception dealing with, java exception hierarchy, sorts of exception in java, and lots of extra.

What’s Exception Dealing with in Java?

Exception dealing with in java helps in minimizing exceptions and helps in recovering from exceptions. It is likely one of the highly effective mechanisms to deal with runtime exceptions and makes it bug-free. Exception dealing with helps in sustaining the movement of this system. An exception dealing with is outlined as an irregular situation which will occur at runtime and disturb the conventional movement of this system.

Additionally Learn: Java Tutorial for learners

What’s an Exception?

An expectation is an surprising occasion that happens whereas executing this system, that disturbs the conventional movement of the code.

Exception dealing with in java with an instance:

Let’s say,

assertion
assertion
assertion
exception ………… an exception occurred, then JVM will deal with it and can exit the prog.
assertion
assertion
assertion

For dealing with exceptions, there are 2 doable approaches

1. JVM

If an exception just isn’t dealt with explicitly, then JVM takes the accountability of dealing with the exception.

As soon as the exception is dealt with, JVM will halt this system and no extra execution of code will happen

import java.util.*;

class Major {
    public static void important (String[] args) {
        System.out.println(5/0);
        System.out.println("Finish of program!");
	}
}

Runtime Error:

 Exception in thread "important" java.lang.ArithmeticException: / by zero
 at Major.important(File.java:5) 

2. Developer

Builders can explicitly write the implementation for dealing with the exception. As soon as an exception is dealt with, the conventional execution of code will proceed.

Preferable: deal with exceptions to make sure your code will get executed usually.

Java Exception Hierarchy

Exception Hierarchy – Following is the Exception Dealing with in Java dealing with hierarchy.

• Throwable –
  • It’s the root class for the exception hierarchy in java. 
  • It’s within the java.lang bundle.
• Error –
  • Subclass of Throwable.
  • Encompass irregular situation that’s out of 1’s management and depends upon the setting
  • They’ll’t be dealt with and can all the time outcome within the halting of this system.
  • Eg: StackOverFlowError that may occur in infinite loop or recursion
• Exception –
  • Subclass of Throwable.
  • Encompass irregular circumstances that may be dealt with explicitly.
  • If one handles the exception then our code will proceed to execute easily.

Kinds of exception in Java

• Checked Exceptions
  • These exceptions which might be checked at compile-time contains checked exceptions.
  • They’re youngster courses of Exception apart from RuntimeException.
  • This system is not going to compile if they aren’t dealt with.
  • Instance: IOException, ClassNotFoundException, and so on.
• Unchecked Exceptions
  • These exceptions which might be checked at runtime contains unchecked exceptions.
  • They’re youngster courses of RuntimeException.
  • They offer runtime errors if not dealt with explicitly.
  • Instance: ArithmeticException, NullPointerException and so on.

Distinction between Checked and Unchecked Exception

Java Exception Index

Java Exception Key phrases

Exception Dealing with in java is managed through 5 key phrases: strive, catch, throw, throws, and at last. Listed here are 5 key phrases which might be utilized in dealing with exceptions in Java

Java Strive-Catch Block

Strive-catch syntax:

strive{
}
catch(Exception e){
}

public class ExceptionDemo {
	public static void important (String[] args) {
		int a=10;
		for(int i=3;i>=0;i--)
		   strive{
		     System.out.println(a/i);  
		   }catch(ArithmeticException e){
		       System.out.println(e);
		   }
	}
}

Output:

3
5
10
java.lang.ArithmeticException: / by zero 

• strive block comprises the code that may throw an exception. Don’t write something further in strive as statements after the exception is not going to get executed if the exception occurred. Strive should be instantly adopted by catch or lastly block.

public class ExceptionDemo {
	public static void important (String[] args) {
		int a=10;
		for(int i=3;i>=0;i--)
		   strive{
		     System.out.println(a/i);  
		   }
	}
}

Compile-time error:

prog.java:5: error: 'strive' with out 'catch', 'lastly' or useful resource declarations
    strive{
    ^
1 error 

• The catch block is used to catch the exception thrown by statements within the strive block. The catch should observe strive else it’ll give a compile-time error.

public class ExceptionDemo {
	public static void important (String[] args) {
		int a=10;
		for(int i=3;i>=0;i--)
		   strive{
		     System.out.println(a/i);  
		   }
		   System.out.println("between try to catch");
		   catch(ArithmeticException e){
		       System.out.println(e);
		   }
	}
}

Compile Time Error:

prog.java:5: error: 'strive' with out 'catch', 'lastly' or useful resource declarations
    strive{
    ^
prog.java:9: error: 'catch' with out 'strive'
    catch(ArithmeticException e){
    ^
2 errors 

Issues to Keep in mind:

Don’t maintain any code after the assertion which is susceptible to exception. As a result of if an exception occurred, it’ll immediately bounce to the catch or lastly block, ignoring all different statements within the strive block.

class Major {
	public static void important (String[] args) {
         strive
       {
             System.out.println(4/0);
	 //is not going to get printed
             System.out.println("finish of strive!");
        }
catch(ArithmeticException e)
        {
            System.out.println("divide by 0");
        }
    }
}

Output:

divide by 0

• Whereas catching the exception within the catch block, both you possibly can have straight the category of exception or its superclass.

Instance: Actual Exception

class Major {
	public static void important (String[] args) {
        strive{
            System.out.println(4/0);
           }
      
        //ArithmeticException 
        catch(ArithmeticException e){
            System.out.println("divide by 0");
        }
    }
}

Output:

divide by 0

Instance: Superclass of Actual Exception

class Major {
	public static void important (String[] args) {
        strive{
            System.out.println(4/0);
           }
      
        //superclass of ArithmeticException 
        catch(Exception e){
            System.out.println("divide by 0");
        }
     }
}

Output:

divide by 0

Java A number of Catch Block

When you have a number of catches, it’s important to keep the hierarchy from subclass to superclass.

Incorrect:

class Major {
	public static void important (String[] args) {
        strive{
            System.out.println(4/0);
        }catch(Exception e)
        {
            System.out.println("Exception : divide by 0");
        }catch(ArithmeticException e)
        {
            System.out.println("ArithmeticException :divide by 0");
        }
	}
}

Compile-time error:

 prog.java:11: error: exception ArithmeticException has already been caught
        }catch(ArithmeticException e)
         ^
1 error 

Appropriate:

class Major {
	public static void important (String[] args) {
        strive{
            System.out.println(4/0);
        }catch(ArithmeticException e)
        {
            System.out.println("ArithmeticException : divide by 0");
        }catch(Exception e)
        {
            System.out.println("Exception : divide by 0");
        }
   }
}

Output:

ArithmeticException: Divide by 0

Java Nested Strive

When there’s one other strive block inside the strive block:

class Major {
	public static void important (String[] args) {
        strive{
                strive{
                    int[] a={1,2,3};
                    System.out.println(a[3]);
                }
   catch(ArrayIndexOutOfBoundsException e)
                {
                    System.out.println("Out of bounds");
                }
              System.out.println(4/0);
        }
       catch(ArithmeticException e)
        {
            System.out.println("ArithmeticException : divide by 0");
        }
	}
    }

Output:

Out of bounds
ArithmeticException: Divide by 0 

Observe – If we put code of outer strive earlier than interior strive, then if an exception occurred, it’ll ignore the complete interior try to transfer on to its catch block.

class Major {
	public static void important (String[] args) {
        strive{
               System.out.println(4/0);
               strive{
                    int[] a={1,2,3};
                    System.out.println(a[3]);
                }
   catch(ArrayIndexOutOfBoundsException e)
                {
                    System.out.println("Out of bounds");
                }
        }
       catch(ArithmeticException e)
        {
            System.out.println("ArithmeticException : divide by 0");
        }
	}
    }

Output:

ArithmeticException: Divide by 0

Java Lastly Block

Accommodates code that should be executed irrespective of if an exception is thrown or not. It comprises code of file launch, closing connections, and so on.

class Major {
	public static void important (String[] args) {
        strive{
            System.out.println(4/0);
        }catch(Exception e)
        {
            System.out.println(e);       
        }
        lastly
        {
            System.out.println("lastly executed");
        }
        
       	        System.out.println("finish");
	}
}

Output:

java.lang.ArithmeticException: / by zero
lastly executed
finish 

Lastly, will execute even when we don’t deal with exceptions. Earlier than halting this system, JVM checks if there’s a “lastly” block.

class Major {
	public static void important (String[] args) {
        strive{
            System.out.println(4/0);
            
        }lastly
        {
            System.out.println("cleansing.......");
        }
	}
}

Runtime Error:

 Exception in thread "important" java.lang.ArithmeticException: / by zero
 at Major.important(File.java:4) 

Output:

cleansing.......

Java Last vs Lastly vs Finalize

Java Throw Key phrase

It’s a key phrase that’s used to explicitly throw an exception.

We will use throw the place in keeping with our logic an exception ought to happen.

Instance:

public class ExceptionDemo {
	static void canVote(int age){
		if(age<18)
            strive{
                throw new Exception();
            }catch(Exception e){
                System.out.println("you aren't an grownup!");
            }
		else
		   System.out.println("you possibly can vote!");
	}
	public static void important (String[] args) {
		canVote(20);
		canVote(10);
	}
}

Output:

you possibly can vote!
you aren't an grownup! 

Java Throws Key phrase

• Throws key phrase is used when callee doesn’t need to deal with the exception fairly it desires to increase this accountability of dealing with the exception to the caller of the operate.
• Mainly says what kind of exception the code can throw and depends on the caller to deal with it.
• It’s used to deal with checked Exceptions because the compiler is not going to permit code to compile till they’re dealt with.

Instance:

public class ExceptionDemo {
	static void func(int a) throws Exception{
		   System.out.println(10/a);  
	}
	public static void important (String[] args) {
		strive{
		    func(10);
		    func(0);
		}catch(Exception e){
		   System.out.println("cannot divide by zero");
		}
	
	}
}

Output:

1
cannot divide by zero 

If callee can throw a number of exceptions, then all will probably be thrown concurrently.

import java.util.*;

public class ExceptionDemo {
	static void func(int a,int b) throws ArithmeticException, ArrayIndexOutOfBoundsException{
		   System.out.println(10/a); 
		   int[] arr={1,2,3};
		   System.out.println(arr[b]);
	}
	public static void important (String[] args) {
		Scanner in=new Scanner(System.in);
		for(int i=0;i<3;i++){
		strive{
		    func(in.nextInt(),in.nextInt());
    		}catch(ArithmeticException e){
    		   System.out.println("cannot divide by zero");
    		}catch(ArrayIndexOutOfBoundsException e){
    		   System.out.println("Out of bounds!");
    		}
		     }
		
	}
   }

Enter:

2 1
0 1
2 3 

Output:

5
2
cannot divide by zero
5
Out of bounds! 

Java Throw vs Throws

Java Customized Exception

You may create your personal exception and provides implementation as to the way it ought to behave. Your exception will behave like a toddler’s class of Exception.

Syntax:

 class YourException extends Exception{}

• Instance:
  • let’s say, you’re working with an airline firm 
  • You might be within the baggage check-in division and as per guidelines, you possibly can permit 15kg per buyer.
  • So now greater than 15kg of weight is an irregular situation for us or in different phrases its an exception
  • That is our logic-based exception, so we’ll create our customized exception WeightLimitExceeded 
  • As per syntax, it’ll lengthen Exception.
  • We outline the constructor which is able to get invoked as quickly as an exception will probably be thrown
  • We’ve to explicitly throw the exception and therefore we’ll use throw key phrase for that.
  • Utilizing throws key phrase is as per our want. If we’re dealing with an exception the place it’s getting thrown then we will keep away from throws, else we’ll use throws and deal with it within the caller.

Implementation:

import java.util.*;

class WeightLimitExceeded extends Exception{
    WeightLimitExceeded(int x){
        System.out.print(Math.abs(15-x)+" kg : ");
    }
}


class Major {
    void validWeight(int weight) throws WeightLimitExceeded{
        if(weight>15)
            throw new WeightLimitExceeded(weight);
        else
            System.out.println("You might be able to fly!");
    }
    
      public static void important (String[] args) {
        Major ob=new Major();
        Scanner in=new Scanner(System.in);
        for(int i=0;i<2;i++){
            strive{
                ob.validWeight(in.nextInt());
            }catch(WeightLimitExceeded e){
                System.out.println(e);
            }
        }
        
	}
}

Enter:

20
7 

Output:

5 kg : WeightLimitExceeded
You might be able to fly! 

Exception Dealing with in java with technique overriding

Exception Dealing with in Java with Methodology Overriding is an overridden technique that declares to throw an exception and declare that it might throw the identical exception or subtype of that exception.

To deal with the exception in Java, you’ll have to observe three vital guidelines. They’re depicted within the under determine.

Benefits and drawbacks of exception dealing with in java

Benefits of excepting dealing with in java 

• Separating Error-Dealing with Code from “Common” Code
• Propagating Errors Up the Name Stack
• Grouping and Differentiating Error Varieties

Disadvantages of excepting dealing with in java 

• Experiencing pointless overhead
• Not understanding how the appliance actually works
• Filling your logs with noisy occasions
• Lack of ability to deal with what truly issues

This brings us to the tip of this text on exception dealing with in java. We hope that you’re now clear in regards to the idea of exception dealing with in java. In case you want to know extra in regards to the java programming language, then go browsing to our free java on-line course with certificates and energy forward in your profession.

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