Facundo Uferer
1. The 8 Primitive Types in Memory
Java does not use objects for everything. Primitives are raw mathematical values held directly on the execution stack without pointer overhead. They divide into integers, floating point, character, and boolean.
Ideal for raw network I/O buffers or audio streaming where memory conservation is paramount.
2. Type Casting: Widening vs Narrowing
When assigning a small type into a larger one (Widening), Java converts it automatically. But forcing a larger value into a smaller bucket (Narrowing) silently chops off higher bits, causing integer overflow.
The MSB is 1, encoding a negative two's complement integer (-128 + 2 = -126).
3. The Integer Division Trap and Modulo (%)
Operating between integers always results in an integer. 5 / 2 produces 2, not 2.5: the fraction is truncated. The modulo operator (%) captures the integer remainder.
Beware of averages! Summing 3 integers and dividing by 3 loses precision unless dividing by 3.0.
4. Short-Circuit Evaluation (&& and ||)
The && and || operators never evaluate their right operand if the left operand already decides the outcome. This shields against NullPointerException and zero division.
Because the left operand is false in &&, Java stops immediately. Using single & forces evaluation of the right operand, triggering NullPointerException.
5. Immutability and Constants with final
The final keyword locks a variable against reassignment once initialized. For universal constants, combine it with static and use UPPER_SNAKE_CASE naming.
Java Type Best Practices
- Elegir int por defecto: int is optimal for CPU registers; use long only for large IDs or timestamps.
- Cuidado con Narrowing: Narrowing casts silently chop off MSB bits causing unexpected negative numbers.
- Divisiones exactas: To keep decimals, ensure at least one operand is cast to double or has .0.
- Siempre && y ||: Always use short-circuit && and || to avoid NullPointerException.