Methods
Write reusable methods with parameters, return values and overloading.
In Java a function that belongs to a class is called a method. Until you learn about objects, you can write static methods and call them directly from main.
public class Main {
static int square(int x) {
return x * x;
}
public static void main(String[] args) {
System.out.println(square(9));
System.out.println(square(square(2)));
}
}Output
81 16
The method header lists the return type (int), the name, and each parameter with its type. A method that returns nothing uses void.
Several parameters
public class Main {
static double simpleInterest(double principal, double ratePercent, int years) {
return principal * ratePercent * years / 100;
}
static void printReceipt(String item, double amount) {
System.out.printf("%-10s Rs %8.2f%n", item, amount);
}
public static void main(String[] args) {
double interest = simpleInterest(20000, 7.5, 3);
printReceipt("Principal", 20000);
printReceipt("Interest", interest);
printReceipt("Total", 20000 + interest);
}
}Output
Principal Rs 20000.00 Interest Rs 4500.00 Total Rs 24500.00
Overloading
Two methods can share a name if their parameter lists differ. Java picks the right one from the arguments you pass.
public class Main {
static int add(int a, int b) {
return a + b;
}
static double add(double a, double b) {
return a + b;
}
static int add(int a, int b, int c) {
return a + b + c;
}
public static void main(String[] args) {
System.out.println(add(2, 3));
System.out.println(add(2.5, 0.25));
System.out.println(add(1, 2, 3));
}
}Output
5 2.75 6