Understanding Methods

Understanding Methods

1. Why Methods? (beginner)

Method = named reusable work-block (verb!). Avoids copy-paste: write add() once, call 100×. Makes code readable, testable, DRY (Don't Repeat Yourself!).

2. Call Flow (stack!)

public class M {
    static int add(int a, int b) { return a + b; } // definition
    public static void main(String[] args) {
        int s = add(3, 4); // CALL (jump + args 3,4 → a,b!)
        System.out.println(s); // 7
        System.out.println(add(10, 20)); // direct use!
    }
}

Steps: main frame pauses → add frame (a=3,b=4) → returns 7 → main resumes. Args copy by value (primitives!).

3. Method Kinds (preview map!)

Kind	Call style	Example
static	ClassName.m() (no object!)	Math.sqrt(16)
instance	obj.m() (needs object!)	s.length()
void vs return	statement vs value	print() vs add()

4. Beginner Rules

• Define inside class (never inside another method!).
• Call static from static directly; instance needs object (else ERROR!).
• Same name + different params = overloading (legal!).

5. Exam Points

• Define + call-trace with stack — 5 marks, very frequent.
• Static vs instance call — 3 marks, frequent.