Exception in JAVA

Objective: In the previous article Interface in Java we have learned about the Interfaces, Extending Interface and Extending Multiple Interface. In this article we will learn about the Exception in Java.

Exceptions:

In java, exception is an event that disrupts the normal flow of the program. It is an object which is thrown at runtime.

There are two types of Exceptions in Java:

1. 1.Checked Exceptions

2. 2.Unchecked Exceptions

3. 3.Error

1. Checked exception: The classes that extend Throwable class except RuntimeException and Error are known as checked exceptions.     

e.g.IOException, SQLException etc. Checked exceptions are checked at compile-time.

2. Unchecked Exception: The classes that extend RuntimeException are known as unchecked exceptions e.g. ArithmeticException, NullPointerException, ArrayIndexOutOfBoundsException etc. Unchecked exceptions are not checked at compile-time rather they are checked at runtime.

There are given some scenarios where unchecked exceptions can occur. They are as follows:

• ->Arithmetic Expression:

If we divide any number by zero, there occurs an ArithmeticException.

int a=50/0;//ArithmeticException  

• ->Null Pointer Exception:

If we have null value in any variable, performing any operation by the variable occurs an ->NullPointerException

String s=null;  

System.out.println(s.length());//NullPointerException

• ->Number format Exception:

The wrong formatting of any value, may occur NumberFormatException. Suppose I have a string variable that have characters, converting this variable into digit will occur ->NumberFormatException.

String s="abc";  

int i=Integer.parseInt(s);//NumberFormatException  

• ->ArrayINdexOutOfBound Exception:

If you are inserting any value in the wrong index, it would result ArrayIndexOutOfBoundsException as shown below:

int a[]=new int[5];  

a[10]=50; //ArrayIndexOutOfBoundsException  

3. Error: Error is irrecoverable e.g. OutOfMemoryError, VirtualMachineError, AssertionError etc.

Exception Handling in Java:

There are 5 keywords used in java exception handling.

1. 1. try

2. 2. catch

3. 3. finally

4. 4. throw

5. 5. throws