Cast Operators

Cast Operators

1. What Casting Means (beginner)

Cast = convert one type to another with (type) prefix. Needed because Java is strict: int won't silently become byte, double won't fit int without your permission.

2. Widening (safe, auto) vs Narrowing (risky, manual)

int i = 100;
long l = i;        // widening int→long: AUTO, safe (small→big)
double d = 7;      // int→double auto → 7.0
double pi = 3.99;
int x = (int) pi;  // narrowing: MANUAL cast, cuts → 3 (decimal LOST!)
byte b = (byte) 258; // 258 % 256 = 2! (overflow wraps — trap!)
char c = (char) 65;  // 65 → 'A'

Direction	Example	Needs cast?	Data loss?
byte→int→long→float→double	int→double	No (auto)	No
double→int, int→byte	(int)3.99	Yes (type)	Yes (cut/overflow)

3. Beginner Average Fix (classic!)

int total = 7, n = 2;
System.out.println(total / n);          // 3 (int/int trap)
System.out.println((double) total / n); // 3.5 (cast one side → double math!)

4. Object Casting Preview (Module 3)

(Child) parentObj downcast needs check: if (obj instanceof Child) first, else ClassCastException.

5. Exam Points

• Widening vs narrowing + (double)total/n fix — 5-7 marks, very frequent.
• (byte)258 overflow + (int)3.99 truncation — 3-5 marks, favourite traps.