In try-catch block finally block is mandatory
Java try-catch blockJava try blockJava try block is used to enclose the code that might throw an exception. It must be used within the method. Show
If an exception occurs at the particular statement in the try block, the rest of the block code will not execute. So, it is recommended not to keep the code in try block that will not throw an exception. Java try block must be followed by either catch or finally block. Syntax of Java try-catchSyntax of try-finally blockJava catch blockJava catch block is used to handle the Exception by declaring the type of exception within the parameter. The declared exception must be the parent class exception ( i.e., Exception) or the generated exception type. However, the good approach is to declare the generated type of exception. The catch block must be used after the try block only. You can use multiple catch block with a single try block. Internal Working of Java try-catch blockThe JVM firstly checks whether the exception is handled or not. If exception is not handled, JVM provides a default exception handler that performs the following tasks:
But if the application programmer handles the exception, the normal flow of the application is maintained, i.e., rest of the code is executed.
Problem without exception handlingLet's try to understand the problem if we don't use a try-catch block. Example 1TryCatchExample1.java Test it NowOutput: Exception in thread "main" java.lang.ArithmeticException: / by zero As displayed in the above example, the rest of the code is not executed (in such case, the rest of the code statement is not printed). There might be 100 lines of code after the exception. If the exception is not handled, all the code below the exception won't be executed. Solution by exception handlingLet's see the solution of the above problem by a java try-catch block. Example 2TryCatchExample2.java Test it NowOutput: java.lang.ArithmeticException: / by zero rest of the code As displayed in the above example, the rest of the code is executed, i.e., the rest of the code statement is printed. Example 3In this example, we also kept the code in a try block that will not throw an exception. TryCatchExample3.java Test it NowOutput: java.lang.ArithmeticException: / by zero Here, we can see that if an exception occurs in the try block, the rest of the block code will not execute. Example 4Here, we handle the exception using the parent class exception. TryCatchExample4.java Output: java.lang.ArithmeticException: / by zero rest of the code Example 5Let's see an example to print a custom message on exception. TryCatchExample5.java Test it NowOutput: Example 6Let's see an example to resolve the exception in a catch block. TryCatchExample6.java Test it NowOutput: Example 7In this example, along with try block, we also enclose exception code in a catch block. TryCatchExample7.java Test it NowOutput: Exception in thread "main" java.lang.ArithmeticException: / by zero Here, we can see that the catch block didn't contain the exception code. So, enclose exception code within a try block and use catch block only to handle the exceptions. Example 8In this example, we handle the generated exception (Arithmetic Exception) with a different type of exception class (ArrayIndexOutOfBoundsException). TryCatchExample8.java Test it NowOutput: Exception in thread "main" java.lang.ArithmeticException: / by zero Example 9Let's see an example to handle another unchecked exception. TryCatchExample9.java Test it NowOutput: java.lang.ArrayIndexOutOfBoundsException: 10 rest of the code Example 10Let's see an example to handle checked exception. TryCatchExample10.java Test it NowOutput: Is finally block mandatory with try catch?Core Java bootcamp program with Hands on practice
Yes, It is possible to have a try block without a catch block by using a final block. As we know, a final block will always execute even there is an exception occurred in a try block, except System. exit() it will execute always.
Is finally block necessary?But finally is useful for more than just exception handling — it allows the programmer to avoid having cleanup code accidentally bypassed by a return , continue , or break . Putting cleanup code in a finally block is always a good practice, even when no exceptions are anticipated.
Can a Finally block exist without a try block?Finally cannot be used without a try block. The try block defines which lines of code will be followed by the finally code. If an exception is thrown prior to the try block, the finally code will not execute. The finally block always executes when the try block exits.
Is it mandatory to use catch with try?Is it necessary that each try block must be followed by a catch block? It is not necessary that each try block must be followed by a catch block. It should be followed by either a catch block or a finally block. And whatever exceptions are likely to be thrown should be declared in the throws clause of the method.
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