In this article, we will discuss checked and unchecked exception in detail with explanation & examples and also list some of most commonly known checked & unchecked exception

Checked Exception:

Exception which are checked at compile-time during compilation is known as Checked Exception
Alternate definition: any line of code that could possibly throw exception, and if it is raised to handle during compilation is said to be checked exception
For example, accessing a file from remote location could possibly throw file not found exception
It is the programmer’s responsibility to handle the checked exception for successful compilation
This way, if any exception is raised during execution then respective handling code will be executed
Note: if it isn’t handled then program will throw compile-time error
Example: IOException, FileNotFoundException, InterruptedException, SQLException, etc
Except Runtime exception & its child classes and error & its child classes, all other exception falls under the category of Checked Exception

CheckedException.java

package in.bench.resources.exception.handling;

import java.io.BufferedReader;
import java.io.FileReader;

public class CheckedException {

	public static void main(String[] args) {

		FileReader fileReader = new FileReader(
				"F:\\BenchRes.txt");
		BufferedReader bufferedReader = 
				new BufferedReader(fileReader);    

		// logic for reading     
	}
}

Output:

Compile-time error: Unhandled exception type FileNotFoundException

Checked exception screen-capture from Eclipse IDE:

Possible solution:

Provide/surround with try-catch block or
add throws clause in method signature at the end

Unchecked Exception:

Exception which are NOT checked at compile-time is known as Unchecked Exception
Alternate definition: any line of code that could possibly throw exception at runtime is said to be unchecked exception
Unchecked exception are because of programming-error
For example, accessing out of index-position to assign some value during execution could possibly throw exception at runtime
So, it is again programmer’s responsibility to handle unchecked exception by providing alternate solution in the exception handling code
Note: if it isn’t handled properly then program will terminate abnormally at runtime
Example: Runtime exception & its child classes and error & its child classes are examples of Unchecked Exception
Like ArithmeticException, NullPointerException, NumberFormatException, ArrayIndexOutOfBoundsException, StatckOverflowError, etc

UncheckedException.java

package in.bench.resources.exception.handling;

public class UncheckedException {

	public static void main(String[] args) {

		char[] ch = new char[4];
		ch[7] = 'B';

		System.out.println(ch);
	}
}

Output:

Exception in thread "main" 
java.lang.ArrayIndexOutOfBoundsException: 7
	at in.bench.resources.exception.handling
	.UncheckedException.main(UncheckedException.java:8)

Unchecked exception screen-capture from Eclipse IDE:

Possible solution:

First of all, find out what possible Exception/Error program can be thrown during execution
Then handle those exception either by surrounding with try-catch block or adding throws declaration at the end of method signature, as per business/programming convenience

Misconception about checked and unchecked exception:

Sometimes, checked exception are also referred as compile-time exception and unchecked exception are referred as runtime exception
But this is mis-leading because every exception (whether it is checked or unchecked) occurs/raised only at the runtime i.e.; during program execution only
Reason: during compilation; checked exception are caught and raises compile-time error, due to which programmer has to handle the exception by providing either try-catch blocks or using throws keyword
Whereas unchecked exception aren’t caught during compilation, rather it raises exception during execution because of programming error

References:

Read Also:

Happy Coding !!
Happy Learning !!

BenchResources.Net

Java tutorial for beginners

Checked Exception v/s Unchecked Exception

Checked Exception:

Unchecked Exception:

Misconception about checked and unchecked exception:

Checked Exception:

Unchecked Exception:

Misconception about checked and unchecked exception:

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