Conditions with if and switch
Branch your program with if, else if, the ternary operator and switch.
An if statement runs its block only when the condition in brackets evaluates to true. In Java the condition must be a real boolean; numbers are not accepted.
public class Main {
public static void main(String[] args) {
int speed = 72;
int limit = 60;
if (speed > limit) {
System.out.println("Slow down! You are " + (speed - limit) + " km/h over.");
} else {
System.out.println("Speed OK.");
}
}
}Output
Slow down! You are 12 km/h over.
else if and logical operators
An else if chain tests each condition from top to bottom and runs only the first block whose condition is true:
public class Main {
public static void main(String[] args) {
int year = 2024;
boolean leap = (year % 4 == 0 && year % 100 != 0) || year % 400 == 0;
if (leap) {
System.out.println(year + " is a leap year");
} else if (year % 2 == 0) {
System.out.println(year + " is even but not a leap year");
} else {
System.out.println(year + " is an ordinary year");
}
}
}Output
2024 is a leap year
The ternary operator
For a simple either-or choice, condition ? valueIfTrue : valueIfFalse fits on one line.
public class Main {
public static void main(String[] args) {
int stock = 0;
String label = stock > 0 ? "In stock" : "Sold out";
System.out.println(label);
}
}Output
Sold out
switch expressions
Modern Java (14 and newer) lets switch produce a value using arrows. There is no fall-through, so no break is needed.
public class Main {
public static void main(String[] args) {
String planet = "Mars";
int moons = switch (planet) {
case "Earth" -> 1;
case "Mars" -> 2;
case "Venus", "Mercury" -> 0;
default -> -1;
};
System.out.println(planet + " has " + moons + " moons");
}
}Output
Mars has 2 moons