Exception Dealing with in Java with Examples

Exception dealing with in java is among the highly effective mechanisms to deal with runtime errors attributable to exceptions. Exception dealing with performs an vital position in software program improvement. This text helps you perceive java exception, exception in java, java exception dealing with, java exception hierarchy, kinds 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 among the highly effective mechanisms to deal with runtime exceptions and makes it bug-free. Exception dealing with helps in sustaining the move of this system. An exception dealing with is outlined as an irregular situation that will occur at runtime and disturb the traditional move of this system.

Additionally Learn: Java Tutorial for newcomers

What’s an Exception?

An expectation is an sudden occasion that happens whereas executing this system, that disturbs the traditional move 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 attainable approaches

1. JVM

If an exception just isn’t dealt with explicitly, then JVM takes the duty 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 Primary {
    public static void foremost (String[] args) {
        System.out.println(5/0);
        System.out.println("Finish of program!");
	}
}

Runtime Error:

 Exception in thread "foremost" java.lang.ArithmeticException: / by zero
 at Primary.foremost(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 traditional 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 package deal.
• Error – 
  • Subclass of Throwable.
  • Include irregular situation that’s out of 1’s management and depends upon the setting
  • They’ll’t be dealt with and can at all times consequence within the halting of this system.
  • Eg: StackOverFlowError that may occur in infinite loop or recursion
• Exception –
  • Subclass of Throwable.
  • Include irregular situations that may be dealt with explicitly.
  • If one handles the exception then our code will proceed to execute easily.

Sorts of exception in Java

• Checked Exceptions
  • These exceptions which are checked at compile-time includes checked exceptions.
  • They’re youngster lessons of Exception aside from RuntimeException.
  • This system won’t compile if they aren’t dealt with.
  • Instance: IOException, ClassNotFoundException, and many others.
• Unchecked Exceptions
  • These exceptions which are checked at runtime includes unchecked exceptions.
  • They’re youngster lessons of RuntimeException.
  • They provide runtime errors if not dealt with explicitly.
  • Instance: ArithmeticException, NullPointerException and many others.

Distinction between Checked and Unchecked Exception

Java Exception Index

Java Exception Key phrases

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

Java Strive-Catch Block

Strive-catch syntax:

strive{
}
catch(Exception e){
}

public class ExceptionDemo {
	public static void foremost (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 incorporates the code which may throw an exception. Don’t write something additional in strive as statements after the exception won’t get executed if the exception occurred. Strive should be instantly adopted by catch or lastly block.

public class ExceptionDemo {
	public static void foremost (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 would give a compile-time error.

public class ExceptionDemo {
	public static void foremost (String[] args) {
		int a=10;
		for(int i=3;i>=0;i--)
		   strive{
		     System.out.println(a/i);  
		   }
		   System.out.println("between attempt 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 Bear in mind:

Don’t hold any code after the assertion which is susceptible to exception. As a result of if an exception occurred, it would right away soar to the catch or lastly block, ignoring all different statements within the strive block.

class Primary {
	public static void foremost (String[] args) {
         strive
       {
             System.out.println(4/0);
	 //won't 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 may have immediately the category of exception or its superclass.

Instance: Precise Exception

class Primary {
	public static void foremost (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 Precise Exception

class Primary {
	public static void foremost (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

In case you have a number of catches, you must keep the hierarchy from subclass to superclass.

Incorrect:

class Primary {
	public static void foremost (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 

Right:

class Primary {
	public static void foremost (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 may be one other strive block inside the strive block:

class Primary {
	public static void foremost (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 

Notice – If we put code of outer strive earlier than interior strive, then if an exception occurred, it would ignore your entire interior attempt to transfer on to its catch block.

class Primary {
	public static void foremost (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 regardless of if an exception is thrown or not. It incorporates code of file launch, closing connections, and many others.

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

Runtime Error:

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

Output:

cleansing.......

Java Ultimate vs Lastly vs Finalize

Java Throw Key phrase

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

We are able to use throw the place in response to 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 may vote!");
	}
	public static void foremost (String[] args) {
		canVote(20);
		canVote(10);
	}
}

Output:

you may 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 moderately it needs to increase this duty of dealing with the exception to the caller of the perform.
• Principally 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 won’t enable 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 foremost (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 likely 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 foremost (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 possibly can create your personal exception and provides implementation as to the way it ought to behave. Your exception will behave like a baby’s class of Exception.

Syntax:

 class YourException extends Exception{}

• Instance:
  • let’s say, you might be working with an airline firm 
  • You might be within the baggage check-in division and as per guidelines, you may enable 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 would lengthen Exception.
  • We outline the constructor which can get invoked as quickly as an exception will likely be thrown
  • We’ve to explicitly throw the exception and therefore we are going to 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 are able to keep away from throws, else we are going to 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 Primary {
    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 foremost (String[] args) {
        Primary ob=new Primary();
        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 will possibly 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 Sorts

Disadvantages of excepting dealing with in java 

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

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

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