Methods in Java

What is a method

A method is a named block of code that performs a task. You write it once and call it whenever you need it, avoiding repeated code. Even main is a method. Methods break a big program into small, reusable, easy-to-read pieces.

Defining a method

public class Main {
    static void greet() {
        System.out.println("Hello!");
    }
    public static void main(String[] args) {
        greet();      // call the method
        greet();      // call again
    }
}

We define greet() once, then call it twice from main. The code inside runs each time it is called.

Parameters

static void greet(String name) {
    System.out.println("Hello, " + name);
}
// call:
greet("Aman");
greet("Diya");

Parameters let you pass information in. name is a parameter; "Aman" is the argument you pass. The method uses whatever value it receives.

Returning a value

static int add(int a, int b) {
    return a + b;
}
// call:
int sum = add(5, 3);
System.out.println(sum);

A method can send a value back with return. Its return type (int) must match. Here add returns the sum, which we store in sum.

void vs return

• void — the method does something but returns nothing (like printing). No return value.
• return type — the method gives a value back (like int, String) using return.

Choose void when the method just performs an action, and a return type when you need a result from it.

Static methods

static int square(int n) {
    return n * n;
}
// called without an object:
System.out.println(square(4));   // 16

A static method belongs to the class, so you can call it directly (like square(4)) without creating an object. main is static, so it can call other static methods directly.

Common mistakes

• Return type mismatch. A method declared int must return an int.
• Forgetting return. A non-void method must return a value on every path.
• Wrong argument count or type. Arguments must match the parameters.
• Calling non-static from static without an object. A static main cannot call a non-static method directly.

Summary

• A method is a reusable named block of code for one task.
• Parameters take input; arguments are the values you pass.
• Use return to send a value back; the return type must match.
• void returns nothing; a return type gives a value.
• static methods are called on the class without an object.

Next, learn reuse with the same name in overloading vs overriding, or the static keyword.