Traffic Signal Using Switch in Java
beginner· Control Flow · Switch Statement
Problem
A switch statement maps each of the three fixed signal colors directly to the action a driver should take.
Given a traffic signal color, print the corresponding driving action.
Input
signal = "Yellow"
Output
Get ready
Java Program
Java
public class TrafficSignalSwitch {
public static void main(String[] args) {
String signal = "Yellow";
String action;
switch (signal) {
case "Red":
action = "Stop";
break;
case "Yellow":
action = "Get ready";
break;
case "Green":
action = "Go";
break;
default:
action = "Invalid signal"; // required so action is always assigned
}
System.out.println(action);
}
}Output
Get ready
Core Logic
Matching the signal color against each case picks out the matching driving action directly.
How It Works
- 1
switch (signal)matches the color string against each case label. - 2"Red" resolves to "Stop", "Yellow" to "Get ready", and "Green" to "Go".
- 3The
defaultcase handles any color outside those three, printing "Invalid signal".
For
signal = "Yellow", the case "Yellow" branch matches directly and prints "Get ready".💡
Key Point: Only three colors ever need a case here — a real traffic controller would also need to handle timing between them, which this simplified lookup doesn't model.
Key Concepts
switch statementString switchdefault case