The author meant to express that we should compute a value of numLetters for each day. Throw new IllegalStateException("Wat: " + day) Įxpressing this as a statement is roundabout, repetitive, and error-prone. Many existing switch statements are essentially simulations of switch expressions, where each arm either assigns to a common target variable or returns a value: int numLetters For example, in the following code, the many break statements make it unnecessarily verbose, and this visual noise often masks hard to debug errors, where missing break statements would mean accidental fall through. The break statements are necessary because without them, statements in switch blocks fall through: All statements after the matching case label are executed in sequence, regardless of the expression of subsequent case labels, until a break statement is encountered. Whilst this traditional control flow is often useful for writing low-level code (such as parsers for binary encodings), as switch is used in higher-level contexts, its error-prone nature starts to outweigh its flexibility. The current design of Java's switch statement follows closely languages such as C and C++, and supports fall through semantics by default. ![]() These include the default control flow behavior between switch labels (fall through), the default scoping in switch blocks (the whole block is treated as one scope), and the fact that switch works only as a statement, even though it is often more natural to express multi-way conditionals as expressions. MotivationĪs we prepare to enhance the Java programming language to support pattern matching (JEP 305), several irregularities of the existing switch statement - which have long been an irritation to users - become impediments. To yield a value from a switch expression, the break with value statement is dropped in favor of a yield statement. Based on that feedback, this JEP makes one change to the feature: Note: Until Java-6, switch case argument cannot be of String type but Java 7 onward we can use String type argument in Switch Case. Feedback was sought initially on the design of the feature, and later on the experience of using switch expressions and the enhanced switch statement. In case, if it is not at the end, then a break statement must be kept after the default statement to omit the execution of the next case statement. They were targeted to JDK 12 in August 2018 as a preview feature. In this case, it's the switch - because the default switch behavior falls through. Switch expressions were proposed in December 2017 by JEP 325. The break applies to the inner-most thing which can be break'd (without a label). If break is excluded from the default case, then the proceeding cases will be reevaluated. ![]() This is a preview language feature in JDK 13. The default case appears to always be evaluated last. These changes will simplify everyday coding, and prepare the way for the use of pattern matching (JEP 305) in switch. > labels (with no fall through), with a further new statement for yielding a value from a switch expression. : labels (with fall through) or new case. ![]() Extend switch so it can be used as either a statement or an expression, and so that both forms can use either traditional case.
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