j21-switch - Blog of Vincent VAUBAN

🧠 Switch Expressions in Java
— Illustrated with French Poets Across Centuries

Like all expressions, switch expressions in Java evaluate to a single value. This value can be used directly in assignments or output statements.
Starting with Java 14, we can use the more concise and safer case L -> labels. These eliminate the need for break statements and make the code easier to read and less error-prone. When needed, you can also use yield in a block to return a value.
📖 For the design motivation behind this feature, see JEP 361.

🎨 Example Scenario — Poets and Their Centuries
Let’s say you’re working with an enum of famous French poets, and you want to determine the century in which each poet lived and wrote.

🐢 Classic Switch Statement
Here's how this might look using a traditional switch statement to determine a poet’s century:

👎 Downsides of the classic approach:
🟣 You have to declare and mutate a variable (century).
🟣 You must remember to add break statements — forgetting one could cause fall-through bugs.

⚡ Modern Switch Expression
With switch expressions, this becomes much cleaner and less error-prone:

🧾 Why It’s Better
🟣 Each case is followed by ->, which directly points to a returned value.
🟣 No need for break.
🟣 The whole construct is an expression, which means you can assign or return it inline.
🟣 It's safe by design — no fall-through means fewer bugs.

📌 Summary
✅ case L -> is called a switch labeled rule.
🟣 Avoids the need for break.
🟣 Prevents accidental fall-through.
🟣 Can be used in both expressions and statements.
🟣 Makes your code cleaner, safer, and more expressive.

🧠 Switch Expressions in Java

Like all expressions, switch expressions in Java evaluate to a single value. This value can be used directly in assignments or output statements.

Starting with Java 14, we can use the more concise and safer case L -> labels. These eliminate the need for break statements and make the code easier to read and less error-prone. When needed, you can also use yield in a block to return a value.

📖 For the design motivation behind this feature, see JEP 361.

🎨 Example Scenario — Poets and Their Centuries

Let’s say you’re working with an enum of famous French poets, and you want to determine the century in which each poet lived and wrote.

🐢 Classic Switch Statement

Here's how this might look using a traditional switch statement to determine a poet’s century:

👎 Downsides of the classic approach:

🟣 You have to declare and mutate a variable (century).

🟣 You must remember to add break statements — forgetting one could cause fall-through bugs.

⚡ Modern Switch Expression

With switch expressions, this becomes much cleaner and less error-prone:

🧾 Why It’s Better

🟣 Each case is followed by ->, which directly points to a returned value.

🟣 No need for break.

🟣 The whole construct is an expression, which means you can assign or return it inline.

🟣 It's safe by design — no fall-through means fewer bugs.

📌 Summary

✅ case L -> is called a switch labeled rule.

🟣 Avoids the need for break.

🟣 Prevents accidental fall-through.

🟣 Can be used in both expressions and statements.

🟣 Makes your code cleaner, safer, and more expressive.