Exceptions & Its Handling

What’s this Exception ,[object Object],Class Test { public static void main(String[] args) { System.out.println( 6/0 ); System.out.println( “Hello” ); // do something else } } Exception in thread "main" java.lang.ArithmeticException: / by zero at NewClass.main(NewClass.java:20)

Throwing an Exception ,[object Object],[object Object]

Understanding the Call Stack ,[object Object],[object Object],[object Object],[object Object],y(), where exception occured x() main() Class Test { public static void main(String[] args) { x(); } void x() { y(); } void y() { int a = 7/0; } }

Exception Handler ,[object Object],[object Object],[object Object],[object Object]

Searching for the Exception Handler in the call stack ,[object Object],y(), where exception occured x() main() throws exception should handle but may forward exception Looking for appropriate handler Looking for appropriate handler should handle but may forward exception

Catch or Specify Requirement ,[object Object],[object Object],[object Object],[object Object],[object Object]

Exception Types : 3 ,[object Object],[object Object],[object Object],UnChecked Exception

Class Hierarchy java.lang.Object java.lang.Throwable java.lang.Error java.lang.Exception java.lang.RuntimeException

Checked Exception ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Runtime Exception ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Error ,[object Object],[object Object],[object Object],[object Object]

Runtime Exception due to Logical Errors public class NewClass { public static void main(String[] args) { int array[] = {6,7,8,9,10}; for(int index=0; index<array.length+2; index++) System.out.print(array[index]+” “); System.out.println("After loop"); } } 6 7 8 9 10 Exception in thread "main"java.lang.ArrayIndexOutOfBoundsException: 5 at NewClass.main(NewClass.java:22)

Runtime Exception due to Logical Errors ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],1st statement Exception in thread "main" java.lang.NullPointerException at NewClass.main(NewClass.java:21)

Runtime Exception due to improper use of API ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Exception in thread "main" java.lang.NullPointerException at NewClass.main(NewClass.java:30) new thread new thread new thread new thread new thread new thread new thread new thread new thread new thread

Runtime Exception due to improper use of API ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],First statement Exception in thread "main" java.lang.ClassCastException: java.lang.String at Test.m(NewClass.java:27) at Test.main(NewClass.java:21)

Dealing with Exception ,[object Object],public class NewClass { public static void main(String[] args) { int array[] = {6,7,8,9,10}; try{ for(int index=0; index<array.length+2; index++) } catch(Exception e) { System.out.println(“Element with this index doen’t exist”); } System.out.print(array[index]+” “); System.out.println("After loop"); } }

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Using finally block ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

java.lang.Object java.lang.Throwable java.lang.Exception java.lang.RuntimeException IndexOutOfBoundsException ArrayIndexOutOfBoundsException StringIndexOutOfBoundsException

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Handling Checked Exceptions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],try{ } catch(FileNotFoundException e) { //….. } throws FileNotFoundException try{ } catch(IOException e) { //….. } throws FileNotFoundException

Creating Custom UnChecked Exceptions public class NewClass { public static void main(String[] args) { m(); } static void m() { throw new MyException(); } } class MyException extends RuntimeException { MyException() { super("This is my exception"); } } Exception in thread "main" Pack.MyException: This is my exception at NewClass.m(NewClass.java:24) at NewClass.main(NewClass.java:20)

Creating Custom Checked Exceptions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Exceptions & Its Handling

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