What Is the Use of Default in Switch Statement

por lucasvictor

17 de abril de 2022

The following rules apply to a switch statement – Another interesting point is the break statement. Each break statement terminates the bounding switch statement. The control flow continues with the first instruction after the switch block. Break statements are necessary because without them, statements in switch blocks fail: all statements after the corresponding case label are executed one after the other, regardless of the expression of the following case labels, until a break statement is found. The SwitchDemoFallThrough program displays faulty instructions in a switch block. The program displays the month corresponding to the entire month and the months that follow in the year: the prerequisite for a final standard clause is defensive programming. This clause must either take appropriate action or include an appropriate commentary on the reasons why no action is taken. Note: Sometimes, if the default value is not placed at the end of the switch case program, we must use the break statement with the default case. The only case I can think of when using NOT default is when the switch checks something where it is quite obvious that any other alternative can be happily ignored The optional break statement associated with each case label ensures that the program exits the switch once the corresponding instruction is executed, and continues to execute the instruction after the switch. If the break is omitted, the program continues to run on the next statement in the switch statement. The break statement is not required if it is preceded by a return statement. If failover operations are enumeration values, you cannot have a default case, receive a warning from the compiler if you miss cases. If new enumeration values are added in the future and you forget to add cases for those values in the switch, you can learn more about the problem at compile time.

You should always ensure that your code performs the appropriate action on unmanaged values if an invalid value has been converted to the enumeration type. Therefore, it may work better for simple cases where you can return to the enumeration box instead of interrupting it. At least it`s not mandatory in Java. According to JLS, he says there may be at most one standard case. This means that no standard case is acceptable. Sometimes it also depends on the context in which you are using the switch statement. For example, in Java, the following switch block does not require default case Switch cases should almost always be case sensitive. For example, suppose each condition initializes a pointer. But if the default case is to occur and we do not initialize in this case, it is possible to land with a zero pointer exception. Therefore, it is recommended to use a standard case statement, even if it can be trivial. Although you can avoid compilation errors for the above method without being the default case by having only one return statement at the end, specifying the default case makes it more readable.

Having a default clause when it`s not really necessary is defensive programming that usually results in code that is too complex due to too much error-handling code. This error handling and detection code affects the readability of the code, makes maintenance difficult, and ultimately results in more errors than it solves. The switch case statement evaluates a specific expression and executes the statements associated with it based on the valued value (which corresponds to a particular condition). Basically, it is used to perform different actions according to different conditions (cases). If the powered-on variable is equal to a case, the instructions that follow that case are executed until a break statement is reached. The default statement is executed when no constant expression value is equal to the value of the expression. If there is no default statement and no case-sensitive match is found, none of the instructions in the switch text are executed. There can be at most one standard statement.

The standard statement does not need to be at the end. It can appear anywhere in the body of the switch statement. A case-sensitive or default label can only be displayed in a switch statement. The body of a switch statement is called a switch block. An instruction in the switch pad can be labeled with one or more case-sensitive or standard labels. The switch statement evaluates its expression and then executes all case-sensitive statements. In the following example, when expr evaluates Bananas, the program matches the value with the case of Bananas and executes the corresponding statement. When a pause occurs, the program exits the switch and executes the instruction after the switch. If the break was omitted, the declaration for the case of “cherries” would also be executed. The three switch body statements in this example are executed when c is equal to `A`, because no break statement is displayed until the following case. Execution control is applied to the first statement (capital_a++;) and continues in order through the rest of the body.

If it is equal to `a`, letter_a and totally increased. Only the sum is increased if c is not equal to “A” or “a”. Final switching instructions: These switch instructions cover all possible values, such as . B as a switch statement on a list of note system types. At the first code development, it is easy to cover all values. However, since we are human beings, there is a small chance of forgetting some of them. If you later add an enumeration value so that all switch statements must be adjusted to make them complete again, the path to the error hell opens. The simple solution is a static code analysis tool. The tool should check all switch statements and check if they are exhaustive or if they have a default value. The following is an example of a comprehensive switching statement. First, we need an enumeration: each code adds complexity.

Testing and documentation shall also be carried out for this purpose. So it`s always good to be able to program with less code. My opinion is that I use a standard clause for non-exhaustive switching instructions, while I do not use a standard clause for exhaustive switching instructions. To make sure I`ve done things right, I use a static code analysis tool. So let`s get into the details: this advice is outdated because it is not based on currently relevant criteria. The glaring omission is what Harlan Kassler said: Does this language depend? I don`t remember the language I was using at the time – maybe that`s true for some languages and not others? A model clause; If specified, this clause is executed if the value of the expression does not match any of the Case clauses. So I believe that if the standard is not to be reached, you do not need to add it. Just one more thing. If we still use a standard clause, the static code analysis tool may not be able to detect exhaustive or non-exhaustive switch statements because it still recognizes the default clause. This is very bad because we are not informed if we extend the enumeration by another value and forget to add it to a switch statement. NOTE: This example checks whether the expression of the switch statement is null. To prevent a NullPointerException from being thrown, make sure that the expression of a switch statement is not null.

A switch statement can have an optional default case that must be displayed at the end of the switch. .