15 – Exception Handling in Java

Selenium Class 15 – Exception Handling in Java

Exception Handling:

• An exception is an event that occurs during execution of a program when normal execution of the program is interrupted.
• Exception handling is a mechanism to handle run-time errors

In Automated Testing Selenium with Java we may face two types’ exceptions

1) Global Exceptions (Ex: ArithmeticException)
2) Local Exceptions (Ex: NoSuchElementException)

Common Scenarios where Exception may occur

1) Scenario where Arithmetic Exception may occur

If we divide any number by zero then ArithmeticException occurs

Ex:
int a=10/0;

2) Scenario where NumberFormat Exception occurs

The wrong format of any value

String s1=”abc”;
String s2=”123″;

int a= Integer.parseInt(s1);
int a= Integer.parseInt(s2);

System.out.println(a); //NumberFormatException

3) Scenario where NullPointerException occurs

String s=null;
System.out.println(s.length()); //NullPointerException

4) Scenario where ArrayIndexOutOfBoundsException occurs

if we assign any value in the wrong index of an Array

Ex:
int [] a= new int[3];
.
.
.
int a[7]=70;
System.out.println(a[7]); //ArrayIndexOutOfBoundsException

Program with Exception (Run-time Error):

int a=10;
int b=0;

int result=a/b;
System.out.println(result);
System.out.println(“Hello Java”);
System.out.println(“Hello Selenium”);

Use try catch block

Syntax:

try {
Statements
…………..
…………..
…………..
catch (ExceptionName name){
exception Handling code
}

Java Program with Exception handling code

int a=10;
int b=0;

try {
int result=a/b;
System.out.println(result);
}
catch (ArithmeticException e1){
System.out.println(“Divided by Zero Error”);
}
System.out.println(“Hello Java”);
System.out.println(“Hello Selenium”);

Handle multiple exceptions

int a=10;
int b=0;
int result;
int [] array1= new int[4];
try {
result=a/b;
System.out.println(result);
}
catch (ArithmeticException e1){
System.out.println(“Divided by Zero Error”);
}
System.out.println(“Hello Selenium”);
try {
array1[1]=100;
System.out.println(array1[10]);
}
catch (ArrayIndexOutOfBoundsException e2){
System.out.println(“Array Out of Bound Error”);
}
System.out.println(“Hello Java World”);

Types of Output in Java

The Output in Computer Programming is basically four types

1) Value based Result/Output (Fixed)
2) Boolean / Logical Result (true/false)
3) Constant based Result
4) Dynamic Result

1) Value based Result/Output (Fixed)

Arithmetic Operators and some predefined methods return this type of result

Example:
System.out.println(10+3);//13
System.out.println(7*4);//28

System.out.println(Math.max(10, 11));//11

2) Boolean / Logical Result (true/false)

Relational or Comparison Operators return Boolean Results, and some predefined methods also return this type of result

Example:
System.out.println(100 > 90);//true
System.out.println(100 < 90);//false

System.out.println(“ABC”.equals(“abc”));//false
System.out.println(“JAVA”.equals(“JAVA”));//true

3) Constant Based Result

Java Returns Constant based Result for 3-way comparison of numbers

Result Criteria:
if number1 = number2 then 0
if number1 > number2 then 1
if number1 < number2 then -1

Example:
int a=7;
String b=”Abc”;

Integer x=a;

System.out.println(x.compareTo(7));//0
System.out.println(x.compareTo(9)); //-1
System.out.println(x.compareTo(6));//1

4) Dynamic Result

i) Generating Random Numbers
ii) Retrun System Data Etc…

Example:
//Generate Random Numbers
System.out.println(Math.random());

//Return System Date
Date myDate = new Date();
System.out.println(myDate);

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