Defining Methods & Parameters
Define methods, read method signatures, and pass arguments to parameters correctly.
Defining Methods & Parameters is a free Java Academy lesson on CoddyKit — lesson 1 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Java Academy learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.
What is a method
What is a method? A reusable block of code with a signature (name + parameter list + return type). You call a method to perform a task and optionally get a result.
Method signature
Method signature includes: return type (e.g., int), method name (e.g., add), and parameter types with names (e.g., (int a, int b)). Modifiers like public or static adjust access and binding.
Define & call
Define add with two int parameters and return the sum. In main, call the method using arguments.
public class Main {
// Add two integers and return the sum
static int add(int a, int b) {
return a + b;
}
public static void main(String[] args) {
// Call the method with arguments 2 and 3
int result = add(2, 3);
System.out.println("add(2, 3) = " + result);
}
}
Params vs args
Parameters are placeholders in the method; arguments are the actual values you pass on call.
public class Main {
// Greet the user by name (parameter)
static void greet(String name) {
System.out.println("Hello, " + name + "!");
}
public static void main(String[] args) {
// "Alice" is an argument; it is copied into parameter `name`
greet("Alice");
greet("Bob");
}
}
Return vs void
void methods do not return a value; others return the specified type (e.g., double). Use return to send a result back.
public class Main {
// Convert Celsius to Fahrenheit and return the result
static double cToF(double c) {
double f = c * 9.0 / 5.0 + 32.0;
return f;
}
// Print a line (no value returned)
static void line() {
System.out.println("----------");
}
public static void main(String[] args) {
double out = cToF(25.0);
System.out.println("25C -> " + out + "F");
line();
}
}
Params order
Arguments match parameters by position and type. Remember: order matters.
public class Main {
// Compute the area of a rectangle
static int area(int width, int height) {
return width * height;
}
public static void main(String[] args) {
// Argument order must match parameter order by position
int a1 = area(3, 5); // width=3, height=5
int a2 = area(5, 3); // width=5, height=3
System.out.println("area(3,5) = " + a1);
System.out.println("area(5,3) = " + a2);
}
}
Signature check
Quick check: Which is a valid Java method signature?
Recap & next
Recap: You defined methods, passed arguments to parameters, returned values, and understood void. Next: return values in depth and overloading.
Frequently asked questions
Is the “Defining Methods & Parameters” lesson free?
Yes — the full text of “Defining Methods & Parameters” is free to read here on the web, and the Java Academy course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Java Academy course, upgrade to CoddyKit PRO.
What will I learn in “Defining Methods & Parameters”?
Define methods, read method signatures, and pass arguments to parameters correctly. You practise Java Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Java Academy?
No prior experience is required. Java Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 3, so you can start here or from the beginning and move at your own pace.
How long does the “Defining Methods & Parameters” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Java Academy lesson?
Yes. Every Java Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Defining Methods & Parameters
- Return Values & Overloading
- Scope & Lifetime