Method

Method is also called function. A method is a block of code that performs a specific task. You can think of it as a "mini-program" inside your class. Method helps make code reusable, organized, and readable.

Method Syntax

modifier returnType methodName(parameterList) {
    // method body
    return value; // optional, only if returnType is not void
}

• modifier → public, private, protected, static (controls access & usage)
• returnType → type of value returned (int, String, void, etc.)
• methodName → meaningful name (camelCase style, e.g., calculateSum)
• parameterList → input values (zero or more)
• method body → logic inside the { }

Example: A Simple Method

public int add(int a, int b) {
    int sum = a + b;
    return sum;
}

• Method name: add
• Parameters: int a, int b
• Return type: int

Calling a Method

public class Calculator {
    public int add(int a, int b) {
        return a + b;
    }

    public static void main(String[] args) {
        Calculator calc = new Calculator();
        int result = calc.add(5, 3);
        System.out.println("Result: " + result);
    }
}

Method Type

Instance Method (Non-static Method)

• Belongs to an object (instance) of the class.
• Can access both instance variables and static variables.
• Must be called using an object reference.
• Can use the this keyword (refers to the current object).
• Used for behavior that depends on the object's state.

public class Calculator {
    public int add(int a, int b) {
        return a + b;
    }
}

Static Method

• Belong to the class, not an object.
• Called without creating an object.
• Can only access static variables (cannot access instance variables directly).
• Cannot use this (no instance context).
• Used for utility functions that don't depend on object state.

public class MathUtil {
    public static int square(int n) {
        return n * n;
    }

    public static void main(String[] args) {
        System.out.println(MathUtil.square(5));
    }
}

Method Parameters & Return Values

• Parameters: Input values for the method.
• Return Value: What the method gives back.

Example: A method that multiplies two numbers

public int multiply(int x, int y) {
    return x * y;
}

Void method has no return value

public void greet(String name) {
    System.out.println("Hello, " + name);
}

Varargs

Varargs allows you to pass zero or more arguments of the same type to a method.

Syntax: type... parameterName

Inside the method, varargs are treated as an array. int... numbers is actually like int[] numbers.

1. A method can have only one varargs parameter.
2. Varargs parameter must be the last parameter in the method signature.

Example:

public void printAll(String... words) {
    for (String word : words) {
        System.out.println(word);
    }
}

Method Overloading

• Same method name, different parameter list.
• Return type alone cannot distinguish methods.

public int add(int a, int b) {
    return a + b;
}

public double add(double a, double b) {
    return a + b;
}

Pass by Value in Java

• Java always passes a copy of the value to methods.
• For objects, the reference is copied (so the object itself can be modified).

Example with primitive:

public void changeValue(int x) {
    x = 10;
}

public static void main(String[] args) {
    int a = 5;
    new Test().changeValue(a);
    System.out.println(a); // still 5
}

Example with object:

public class Test {
    public void changeName(Person p) {
        p.name = "Alice";
    }

    public static void main(String[] args) {
        Person person = new Person("Bob");
        new Test().changeName(person);
        System.out.println(person.name); // Alice
    }
}