Methods in Java Declaration, Overloading, Recursion: Tutorial, Examples, FAQs & Interview Tips

Method Declaration Syntax

A method is a reusable block of code that performs a specific task. The general syntax is:

Method Syntax

accessModifier returnType methodName(parameterList) {
    // method body
    return value; // if returnType is not void
}

Method Declaration & Overloading

public class Methods {

    // Static method - no object needed
    public static int add(int a, int b) {
        return a + b;
    }

    // Method overloading - same name, different parameters
    public static double add(double a, double b) {
        return a + b;
    }

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

    // void method - no return value
    public static void greet(String name) {
        System.out.println("Hello, " + name + "!");
    }

    public static void main(String[] args) {
        System.out.println(add(3, 4));          // 7   (int version)
        System.out.println(add(1.5, 2.5));      // 4.0 (double version)
        System.out.println(add(1, 2, 3));       // 6   (3-param version)
        greet("Alice");                          // Hello, Alice!
    }
}

Varargs (Variable Arguments)

Varargs let a method accept any number of arguments of the same type. The varargs parameter must be the last parameter and is treated as an array inside the method.

Varargs & Recursion

public class VarargsRecursion {

    // Varargs - accepts 0 or more int arguments
    public static int sum(int... numbers) {
        int total = 0;
        for (int n : numbers) total += n;
        return total;
    }

    // Recursion - factorial
    public static long factorial(int n) {
        if (n <= 1) return 1;          // base case
        return n * factorial(n - 1);   // recursive call
    }

    public static void main(String[] args) {
        // Varargs
        System.out.println(sum());           // 0
        System.out.println(sum(5));          // 5
        System.out.println(sum(1, 2, 3));    // 6
        System.out.println(sum(1,2,3,4,5));  // 15

        // Recursion
        System.out.println(factorial(5));    // 120
        System.out.println(factorial(10));   // 3628800
    }
}

Static vs Instance Methods

Feature	Static Method	Instance Method
Belongs to	The class	An object (instance)
Called with	`ClassName.method()`	`object.method()`
Can access instance fields?	No	Yes
Can access static fields?	Yes	Yes
Typical use	Utility/helper methods	Object behavior

Key Takeaways

Java methods must declare a return type - use void if the method returns nothing.
Method overloading allows multiple methods with the same name but different parameter lists.
Java passes primitives by value and objects by reference (technically, by value of the reference).
Use varargs (String... args) to accept a variable number of arguments.
Static methods belong to the class, not instances - call them with ClassName.method().
Recursive methods must have a base case to prevent infinite recursion and StackOverflowError.

Methods in Java Declaration, Overloading, Recursion: Tutorial, Examples, FAQs & Interview Tips

Method Declaration Syntax

Varargs (Variable Arguments)

Static vs Instance Methods

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