What is exception handling in DART

In this article, i am going to explain about exception handling in DART language.
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Exception Handling  in DART language

DART is designed to facilitate handling of error condition using the same mechanism, based on exception, that is employed by java and  C++. A exception is an event that occur during the execution of program.

In order to deal with possible error condition you will normally divide the relevant part of your program into a number of blocks of three different types:

  • Try block

    Try block contain code that forms part of normal operation of your program, but which might encounter some serious error conditions.
     
  • Catch block

    Catch block are used to handling the exception.
     
  • Finally block

    It is reside at the end of the try block, and it's executed whether error is occurred or not.

Here, some of common built-in  DART exception:

  • IndexOutOfRangeException:

    If you declare a list of size 4 (four) and wants to access it's fifth (5) element, then it gives IndexOutOfRangeException:5.
     
  • NoSuchMethodException

          If you want to access that method which is not given in your code, then NoSuchMethodException:method is found :'Method name' exception is occured.

  • NullPointerException

    NullPointerException is occurred, when you gives a null value to any variable and wants to perform some operation by the help of this variable.
     

Example of exception handling in DART language

void main() {

  var list = [1,2,3,4];

  /**** IndexOutOfRangeException *********/

  try{

    print("Out of range execption................");

    print(" ");

    print(list[5]); //Try to access out of range variable.

   

  }

  catch(IndexOutOfRangeException ex){

    print('The exception is: ${ex}');

  }

  /**** NoSuchMethodException *********/

  try{

    print("");

    print("No such method exception................");

    print("");

    MethodExcep obj = new MethodExcep();

    obj.IllegalMethod(); // you'r trying to access that method,which is not aviable.

  }

  catch(NoSuchMethodException ex){

    print('The exception is: ${ex}');

  }

  /**** NullPointerException*********/

  try{

    print("");

    print("Null pointer exception................");

    print("");

    MethodExcep o = new MethodExcep();

    o.a(null,2); // You want to perform operation on null value.

  }

  catch(NullPointerException ex){

    print('The exception is: ${ex}');

  }

  finally{

    print("All Exception all handled here");

  }

}

class MethodExcep{

  void Legal(){

    print("I am a legal method");

  }

  a(int a, int b)

  {

    int c=a-b;

    print(c);

  }
}


Output:

exception.jpg

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