OCP 17 Exam - chapter 2 notes

Chapter 2 notes

• unary = 1 param, binary = 2 params, ternary = 3 params
• numeric promotions rules:
  • always to larger data type, e.g. short -> int
  • integral type is promoted to floating point if used together,
    • e.g. var z = (double) 1.0 + (short) 1 - result is double
  • smaller types byte, short, char are promoted to int if used in arithmetic ops (+, *, etc.),
    • e.g. short s = 1 + (short)(1 * 2) - doesn’t compile, because 1+ implicitly casts to int
• float y = 2.1 doesn’t compile, because f is required!
• *= automatically casts to smaller type,
  • e.g.long l = 1; int i = 2; i=i*l - doesn’t compile, but long l = 1; int i = 2; i*=l does.
• assignment also returns value, examples:
  • long coyote = (wolf = 3) assigns 3 to wolf and coyote
  • if(healthy = true), assigns true to healthy and satisfies if statement
• equality operators can be used only for the same type,
  • e.g. true == 3 or "3" == 3 doesn’t compile
• instanceof is also limited to the same type or superclass or interited type
  • e.g. Number num = 3; boolean b = num instanceof String; - doesn’t compile, but b = num instanceof java.util.concurrent.atomic.AtomicInteger; does
• null instanceof String always returns false
• XOR truth table:

XOR true ^ true = false
XOR false ^ false = false
XOR true ^ false = true
XOR false ^ true = true

• & always evaluates both operands, where && evaluates right, only when left is true (similar rule applies to | and ||)
  • e.g. int i = 6; boolean b = (i >= 6) || (++i <= 7) - after executing i=6, because left of || was true, so no need to evaluate right side (unperformed side effect)

Playground code

https://github.com/RG9/rg-playground-ocp17/blob/main/Chapter2.java