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Java - switch Statement

📌 What You Will Learn
  • The small building blocks of Java: tokens
  • All 8 primitive data types with their ranges
  • Type casting — implicit and explicit
  • Control statements: if, switch, loops
  • Arrays — single, double and jagged
  • Variable length arguments (var-args)

switch Statement is a core concept of the Java language. This lesson explains switch and switch — The Complete Rules with complete, runnable code examples, clear step-by-step explanations, and common mistakes to avoid with exam-style MCQs at the end.

switch

When you have many fixed values to check, switch is cleaner than many if-else. It selects one case from many.

Example01
JCode Cell
1switch (expression) {
2 case value1: statements; break;
3 case value2: statements; break;
4 ...
5 default: statements; // optional
6}

switch

Trainer's Note: Updated knowledge: In Java 7+, switch supports String values. From Java 14, a modern switch expression lets you write int x = switch(day) { case 1 -> 100; default -> 0; }; — we will study this in the Java 12-14 chapters. Also, break is needed in old-style switch to stop falling into the next case.
Example02
JCode Cell
1class SwitchDemo {
2 public static void main(String[] args) {
3 int day = 3;
4 switch (day) {
5 case 1: System.out.println("Monday"); break;
6 case 2: System.out.println("Tuesday"); break;
7 case 3: System.out.println("Wednesday"); break;
8 default: System.out.println("Some other day");
9 }
10 }
11}
Output
Wednesday

switch — The Complete Rules

switch is perfect for menu-driven programs (like a stack menu: PUSH, POP, PEEK, EXIT). These are the rules from the classic material:

  • Allowed parameter types: byte, short, int, char (and String since Java 7). long, float and double are not allowed.
  • All case values must be constants (including final variables) — ordinary variables are not allowed.
  • Case values must lie within the range of the switch's data type. For byte b, case 128 is an error.
  • Duplicate case values are not allowed.
  • default is optional and can be written anywhere, but convention puts it last.
Example03
JCode Cell
1class SwitchRules {
2 public static void main(String[] args) {
3 String month = "JAN";
4 switch (month) { // String allowed from Java 7
5 case "JAN": System.out.println("January"); break;
6 case "FEB": System.out.println("February"); break;
7 default: System.out.println("Other month");
8 }
9 }
10}
Output
January
📝 Key Takeaways
  • Tokens are the smallest pieces of a program: identifiers, literals, keywords, operators, separators.
  • Java has 8 primitive types: byte, short, int, long, float, double, char, boolean.
  • Widening casting is automatic and safe; narrowing casting needs brackets and may lose data.
  • if / switch decide which path runs; for / while / do-while repeat code; break and continue control loops.
  • Arrays hold many same-type values; index starts at 0; size is fixed; for-each loop reads them simply.
  • Var-args (int... x) lets a method take any number of arguments.

🧠 Test Your Knowledge

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