Casting

int → double   (32-bit → 64-bit: always safe)

int x = 5;
double y = x;   // y = 5.0 (automatic — Java converts int to double)

System.out.println(y);  // Output: 5.0

double price = 9.99;
int rounded = (int) price;   // rounded = 9 (decimal is TRUNCATED, not rounded)

System.out.println(rounded);  // Output: 9

(int) 3.1    // → 3
(int) 3.9    // → 3 (NOT 4!)
(int) -2.7   // → -2 (truncates toward zero)
(int) 99.999 // → 99

double x = 9.99;
int y = x;         // ERROR: incompatible types — possible lossy conversion
int z = (int) x;   // OK: you're telling Java "I know I might lose data"

int a = 7;
int b = 2;

double result1 = a / b;         // result1 = 3.0 (int division first → 3 → stored as 3.0)
double result2 = (double) a / b; // result2 = 3.5 (cast a to double → double division)
double result3 = a / (double) b; // result3 = 3.5 (cast b to double → double division)
double result4 = (double) (a / b); // result4 = 3.0 (int division first → 3 → cast to 3.0)

double price = 3.7;
int rounded = (int) (price + 0.5);  // (int) 4.2 = 4 ✓

double price2 = 3.2;
int rounded2 = (int) (price2 + 0.5); // (int) 3.7 = 3 ✓

int x = 5;
double y = 2.5;
double result = x + y;  // 5 is promoted to 5.0, result = 7.5

char letter = 'A';
int ascii = (int) letter;   // ascii = 65
char next = (char) (letter + 1);  // next = 'B' (66)

int total = 97;
int count = 10;

// WRONG way to get average
double avg1 = total / count;         // avg1 = 9.0 (NOT 9.7)

// RIGHT way to get average
double avg2 = (double) total / count; // avg2 = 9.7

// Also RIGHT
double avg3 = total * 1.0 / count;   // avg3 = 9.7 (multiplying by 1.0 makes it a double)

System.out.println(avg1);  // 9.0
System.out.println(avg2);  // 9.7
System.out.println(avg3);  // 9.7