return statement with finally block

February 18, 2017 SJ Exception Handling 0

In this article, we will discuss whether finally-block always gets executed, even if there is a return statement in try-block or catch-block or both try-catch blocks for valid cases

To discuss this topic, we will consider one of the valid case from previous article i.e.; method returning from try-block & catch-block and it also contains finally-block with some statements i.e.; Case-6 in that article

 

1. Happy Scenario

  • No exception is raised from try-block
  • and value is returned from try-block

ReturnValueExample.java

package in.bench.resources.exception.handling;

public class ReturnValueExample {

	public static void main(String[] args) {

		// invoking static method
		System.out.println(returnValueFromMethod());
	}

	// method enclosed with try-catch-finally blocks
	// and returns-value 
	public static int returnValueFromMethod() {

		int result = 0;

		try {
			result = 18/3;
			return result;
		}
		catch(ArithmeticException aex) {
			System.out.println(aex.toString());
			return -1;
		}
		finally {
			System.out.println("finally block"
					+ " always executed for resource clean-up");
		}
	}
}

Output:

finally block always executed for resource clean-up
6

 

2. Exception Scenario

  • Exception is raised & it is caught in the catch-block
  • and value is returned from catch-block

ReturnValueExample.java

package in.bench.resources.exception.handling;

public class ReturnValueExample {

	public static void main(String[] args) {

		// invoking static method
		System.out.println(returnValueFromMethod());
	}

	// method enclosed with try-catch-finally blocks
	// and returns value 
	public static int returnValueFromMethod() {

		int result = 0;

		try {
			result = 18/0;
			return result;
		}
		catch(ArithmeticException aex) {
			System.out.println(aex.toString());
			return -1;
		}
		finally {
			System.out.println("finally block"
					+ " always executed for resource clean-up");
		}
	}
}

Output:

java.lang.ArithmeticException: / by zero
finally block always executed for resource clean-up
-1

Explanation:

  • In both scenarios i.e.; Happy scenario as well as Exception scenario, finally-block always gets executed

 

Now next question is,

Q) Whether finally-block always executed irrespective of whether exception thrown or NOT and whether it is handled or NOT ?

  • The answer is certainly yes
  • but on one condition finally-block won’t gets executed
  • when program encounters some statement which will kill the program execution further
  • like System.exit(0);

ReturnValueExample.java

package in.bench.resources.exception.handling;

public class ReturnValueExample {

	public static void main(String[] args) {

		// invoking static method
		System.out.println(returnValueFromMethod());
	}

	// method enclosed with try-catch-finally blocks 
	// and returns-value 
	public static int returnValueFromMethod() {

		int result = 0;

		try {
			result = 18/3;
			System.exit(0);
			return result;
		}
		catch(ArithmeticException aex) {
			System.out.println(aex.toString());
			return -1;
		}
		finally {
			System.out.println("finally block"
					+ " always executed for resource clean-up");
		}
	}
}

Explanation:

  • When above program is executed, it doesn’t print anything in the console
  • because it encounters System.exit(0); just before return statement & program terminates

 

Highlight of return statement in finally-block:

It is valid sequence to have return statements in all three blocks i.e.;

  1. try-block
  2. catch-block
  3. finally-block

 

Q) What will happen, when return statement is encountered in finally block ?

  • return-value from try-block for successful execution will be overridden by return-value in the finally-block
  • return-value from catch-block for exception thrown will be overridden by return-value in the finally-block

 

finally-block overrides return-value from try-block and catch-block

  • Let us see 2 examples for this scenario:

Example 1: Successful execution and return statement from try-block

Explanation:

  • Above program execution should return integer-value 6 from try-block
  • But from above program output, it is seen that it is returning integer value 1,
  • because return-value from try-block is overridden when control flows to finally-block
  • As we all know, finally-block always gets executed irrespective of whether exception is raised or NOT & whether that exception is caught or NOT
  • Therefore, any statement inside finally-block will be executed before encountering a return statement
  • Error-scenario : if we keep any statement inside finally-block after return statement or after finally-block, then it raises compile-time error stating “Unreachable code”

 

Example 2: Successful execution and return statement from catch-block

Explanation:

  • Above program execution raises exception as there is a divide by zero calculation inside try-block
  • Exception raised from try-block gets caught in the catch-block and catch-block returns integer value -1
  • But from above program output, it is seen that it is returning integer value 1, because return-value from catch-block is overridden when control flows to finally-block
  • As we all know, finally-block always gets executed irrespective of whether exception is raised or NOT & whether that exception is caught or NOT
  • Therefore, any statement inside finally-block will be executed before encountering a return statement
  • Error-scenario : if we keep any statement inside finally-block after return statement or after finally-block, then it raises compile-time error stating “Unreachable code”

 

References:

 

Read Also:

 

Happy Coding !!
Happy Learning !!

final v/s finally v/s finalize
Returning value from method having try-catch-finally blocks

Related posts:

  1. finally block in Java
  2. throws keyword in Java
  3. try with resources in Java 1.7 version
  4. Difference between throws clause and try-catch-finally block