{"id":171878,"date":"2023-08-11T06:23:51","date_gmt":"2023-08-11T06:23:51","guid":{"rendered":"https:\/\/www.henryharvin.com\/blog\/?p=171878"},"modified":"2024-12-23T10:48:01","modified_gmt":"2024-12-23T10:48:01","slug":"exception-handling-in-java","status":"publish","type":"post","link":"https:\/\/www.henryharvin.com\/blog\/exception-handling-in-java\/","title":{"rendered":"Exception Handling in Java Types and Examples"},"content":{"rendered":"\n

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To begin with, Exception Handling in Java deals with error this occurs when the program is executed. It can also be mentioned as an error that disrupts the normal flow of the program.  Experienced and beginners both encounter this problem, and Java offers an object-oriented way to solve the errors; this is known as exception handling.<\/h2>\n\n\n\n

Further talking about, Exception Handling In Java which occurs during runtime errors and does occur for different reasons. Network connectivity issues, Wrong input data, calling a non-existent file, exceeding the memory limits of the Java virtual machine\u2014there are also various types of Java exceptions, such as those that occur at run time, can\u2019t be handled during compilation time, etc.<\/p>\n\n\n\n

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Types<\/strong><\/h2>\n\n\n\n

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Firstly Exception Handling is of two types: user-defined exceptions and built-in exceptions. The built-in exception has two types: checked and unchecked exceptions.<\/p>\n\n\n\n

Checked exceptions<\/td>Unchecked exceptions<\/td><\/tr>
This shows at compile time<\/td>This shows while executing the program<\/td><\/tr>
The compiler identifies this type of exception<\/td>Because the compiler doesn\u2019t identify this type of exception<\/td><\/tr>
It can be solved during compilation time<\/td>It cannot be identified during compilation time<\/td><\/tr>
Ex: IO Exception<\/td>Ex: Null pointer Exception<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

There are various types of exception handling<\/a> that fall under checked and unchecked exceptions. Now let\u2019s see types under Unchecked Exception<\/strong><\/p>\n\n\n\n

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1. Null pointer exception<\/strong><\/h2>\n\n\n\n

When you call a variable whose value is zero or null, you\u2019ll get a null pointer exception.<\/p>\n\n\n\n

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Below is a sample code<\/strong><\/p>\n\n\n\n

\nBelow is a sample code\n \nclass nullpointerexception\n{\n    public static void main()\n    {\n        String s = null;\n        System.out.println(s.length());\n    }\n}\n \n<\/code><\/pre>\n\n\n\n
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Output:<\/strong><\/p>\n\n\n\n
java. lang.NullPointerException<\/p>\n\n\n\n
The value of the above variable is null and hence we get a null pointer Exception<\/p>\n\n\n\n
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2. Arithmetic Exception<\/strong><\/h2>\n\n\n\n
This type of error occurs when you attempt to run the wrong mathematical operation through code. Under exception Handling in Java, this error is the only one that overlaps with mathematics.<\/p>\n\n\n\n
Ex: Divide any number by zero <\/p>\n\n\n\n
Below is a sample code:<\/strong><\/p>\n\n\n\n
public class ExceptionTest {\n \n  public static void main(String[] args) {\n    try {\n        int divbyzero = 1\/0;\n    }\n    catch (ArithmeticException ex) {\n        ex.printStackTrace();\n        System.out.println (ERROR: Divide by zero\")\n \n<\/code><\/pre>\n\n\n\n
 Output:<\/strong><\/p>\n\n\n\n
The above code is showing an arithmetic error.<\/p>\n\n\n\n
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3. Array Index Out of Bounds Exception<\/strong><\/h2>\n\n\n\n
Few of the Exception Handling In java deal with value. This error occurs when you process an array but call a value in the array which doesn\u2019t exist in the particular array<\/p>\n\n\n\n
\"Exception<\/figure><\/div>\n\n\n\n
Below is a sample code:<\/strong><\/p>\n\n\n\n
 \npublic class Example \n{ public void processArray()\n { List names = new ArrayList<>(); names.add(\"Eric\"); names.add(\"Sydney\"); \nreturn names. get(5); } }\n<\/code><\/pre>\n\n\n\n
output:<\/strong><\/p>\n\n\n\n
ArrayIndexOutOfBoundsException<\/p>\n\n\n\n
The code gives you the above error because you are calling a value that doesn\u2019t exist.<\/p>\n\n\n\n
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4. Runtime exception<\/strong><\/h2>\n\n\n\n
If any kind of exception arises during the execution of the program, it is a Runtime exception<\/p>\n\n\n\n
Below is a sample code<\/strong><\/p>\n\n\n\n
 \npublic class Runtime_Excp_Ex { public void Demo_Runtime_Exception () { throw new Running_Exception(); } public static void main(String[] args) { try { new Running_Exception().Demo_Runtime_Exception(); } catch(Exception excpn) { System.out.println(excpn.getClass().getName()); } } } class Running_Exception extends RuntimeException { public Running_Exception() { super(); } public void Demo_Runtime_Exception() { throw new Running_Exception(); }\n\n\n<\/code><\/pre>\n\n\n\n
Output:<\/strong><\/p>\n\n\n\n
<\/p>\n\n\n\n
The error shows during execution only<\/p>\n\n\n\n
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5. Illegal thread state exception<\/strong><\/h2>\n\n\n\n
 This Exception Handling In java is quite unique as it attempts to show the status of the program. Suppose you attempt to start a thread that is already in running mode and executing its functions It gives you an exception called the illegal thread state exception.<\/p>\n\n\n\n
Below is a Sample code:<\/strong><\/p>\n\n\n\n
public class MyThread extends Thread \/\/ Creating MyThread class that is extending the Thread class\n{\n    public void run() \n    {\n\t  for (int i = 0; i < 3 ; i++)\n\t  {\t\n\t\tSystem.out.println(i);\t\n\t  }\n    }\n\n    public static void main(String args[])\n    {\n        \/\/In main() method, creating a thread object  \n        MyThread th = new MyThread();\n\n        Stating the thread\n        th.start();\n        \n        System.out.println(\"Alive is Awesome\");\n\n        starting the thread again when it's already running, causing an IllegalThreadStateException.\n\n       th.start();\n<\/code><\/pre>\n\n\n\n
output:<\/strong><\/p>\n\n\n\n
        Illegal thread state exception<\/p>\n\n\n\n
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Checked Exceptions<\/strong><\/h2>\n\n\n\n
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1. IO Exception<\/strong><\/h2>\n\n\n\n
This kind of exception occurs while reading file directories and streams. Suppose you are calling a file \u2018input.txt, which has not been declared, then such an exception. Under Exception Handling in Java, this exception deals with name of the files and directories.<\/p>\n\n\n\n
Sample code:<\/p>\n\n\n\n
import java.io.*;\n\/\/ Example of FileNotFoundException\nclass Test{\npublic static void main(String[] args) {\n\/\/ Creating an instance of FileReader class\nFileReader fileReader = new FileReader(\"input.txt\");\nSystem.out.println(fileReader.read());\nfileReader.close();\n}\n}\n<\/code><\/pre>\n\n\n\n
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Output:<\/strong><\/p>\n\n\n\n
Main.java:7: error: unreported exception FileNotFoundException must be caught or declared to be thrown<\/p>\n\n\n\n
    FileReader fileReader = new FileReader(“input.txt”);<\/p>\n\n\n\n
                            ^<\/p>\n\n\n\n
Main.java:8: error: unreported exception IOException must be caught or declared to be thrown<\/p>\n\n\n\n
    System.out.println(fileReader.read());<\/p>\n\n\n\n
                                      ^<\/p>\n\n\n\n
Main.java:9: error: unreported exception IOException must be caught or declared to be thrown<\/p>\n\n\n\n
    fileReader.close();<\/p>\n\n\n\n
                    ^<\/p>\n\n\n\n
It is showing IO Exception<\/p>\n\n\n\n
2. Class not found Exception<\/h2>\n\n\n\n
This Exception occurs when you are calling a class that does not exist.<\/p>\n\n\n\n
Sample code:<\/p>\n\n\n\n
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\/\/ Java Program to Handle Checked Exception\n \nImporting required classes\nimport java.io.*;\n \n\/\/ Main class\nclass GFG {\n \n    \/\/ Main driver method\n    public static void main(String[] args)\n    {\n        \/\/ Calling the class gfg, which is not present in the\n        \/\/ current class temp instance of calling class\n        Class temp = Class.forName(\"gfg\");\n \n        It will throw ClassNotFoundException\n    }\n}\n<\/code><\/pre>\n\n\n\n
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Output:<\/strong><\/p>\n\n\n\n
Here we are calling it  \u2018gfg\u2019 instead of \u2018GFG\u2019.<\/p>\n\n\n\n
\"\"<\/figure><\/div>\n\n\n\n
3. File not Found Exception<\/strong><\/h2>\n\n\n\n
This Exception arises when you try to read data from a particular file under a particular class, but such a file doesn’t exist under the constructor, and this error is shown. Under Exception Handling In Java, this shows how careful you must be whenever you call a class.<\/p>\n\n\n\n
Sample code:<\/p>\n\n\n\n
import java.io.File;\nimport java.io.FileReader;\n\npublic class FilenotFound_Demo {\n\n   public static void main(String args[]) {      \n      File file = new File(\"E:\/\/file.txt\");\n      FileReader fr = new FileReader(file);    \n   }\n}\n<\/code><\/pre>\n\n\n\n
output:<\/p>\n\n\n\n
C:\\>javac FilenotFound_Demo.java<\/p>\n\n\n\n
FilenotFound_Demo.java:8: error: unreported exception FileNotFoundException must be caught or declared to be thrown<\/p>\n\n\n\n
   FileReader fr = new FileReader(file);                      <\/p>\n\n\n\n
      ^<\/p>\n\n\n\n
1 error<\/p>\n\n\n\n
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