OOP

• ▸ oop == vs equals() vs the hashCode contractFREE
• ▸ oop Singleton pattern — 4 ways to implement it, which is thread-safe?FREE
• ▸ oop Composition over inheritance — when extending a class hurts
• ▸ oop SOLID, part 2 — Interface Segregation and Dependency Inversion
• ▸ oop Liskov Substitution — how to spot a violation
• ▸ oop Designing an immutable class — the full checklist
• ▸ oop Constructor, static factory or builder — picking a creation style
• ▸ oop Generics and type erasure — what erasure stops you doing
• ▸ oop Wildcards — ? extends vs ? super and the PECS rule
• ▸ oop Strategy and Template Method in modern Java
• ▸ oop How Java picks an overload — widening, boxing and varargs
• ▸ oop The four pillars of OOP — what each one buys you in Java
• ▸ oop Constructors — default, parameterised and chaining with this() and super()
• ▸ oop Why one superclass but many interfaces?
• ▸ oop Overloading vs overriding — the rules that trip people up
• ▸ oop Compile-time vs runtime polymorphism — what dynamic dispatch really does
• ▸ oop Access modifiers — public, protected, package-private and private
• ▸ oop this and super — every way to use them
• ▸ oop Why clone() is broken — and what to use instead
• ▸ oop Abstract class or interface? Choosing well since Java 8
• ▸ oop Calling an overridable method from a constructor — the half-built object
• ▸ oop Field hiding and static method hiding — why they aren't overriding
• ▸ oop Overriding rules — covariant return types and the throws clause
• ▸ oop Default methods and the diamond problem — how conflicts get resolved
• ▸ oop Static nested, inner, local and anonymous classes — which when?
• ▸ oop Upcasting, downcasting and ClassCastException
• ▸ oop SOLID, part 1 — Single Responsibility and Open/Closed with examples
• ▸ oop instanceof or getClass() in equals? The symmetry trap