☕ JAVA COMPILE-TIME vs RUNTIME RESOLUTION

✅ Compile-Time Resolution (Static Binding)

Happens during compilation.
Direct calls, no lookup, faster.

• Methods:

  • static, private, final, constructors, super calls

• Variables:

  • static variables, final constants, locals, field offsets

• Generics & Types:

  • Type erasure, bounds checking, wildcard resolution, method signatures

• Initialization:

  • Static blocks order, static variable init, class structure, access control

⚡ FASTEST – resolved once, no runtime cost.

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🔄 Runtime Resolution (Dynamic Binding)

Happens during execution.
Allows polymorphism & flexibility.

• Methods:

  • Overridden (virtual) methods, interfaces, abstract methods, lambdas

• Objects & Memory:

  • Object creation, type casting, instanceof, array store checks

• Reflection & Dynamic:

  • Method.invoke(), Field.get/set(), Class.forName(), proxies, annotations

• Collections & Init:

  • Instance blocks, generic cast checks, auto-boxing/unboxing

🔁 FLEXIBLE – enables polymorphism & late binding.

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📝 Quick Examples

Compile-Time:

static final int MAX = 100;   // inlined
private final void helper() {} // fixed

Runtime:

Animal a = new Dog();
a.makeSound();   // dynamic dispatch

Method m = Dog.class.getMethod("makeSound");
m.invoke(a);     // reflection

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📌 Extra Notes

• Performance: Compile-time = fast; Runtime = slower (JIT helps).

• Bytecode Ops:

  • Compile: invokestatic, invokespecial

  • Runtime: invokevirtual, invokeinterface, invokedynamic

• Generics: Checked at compile, erased at runtime → List<T> → List.

• Rule of Thumb:

  • Fixed = Compile-Time

  • Overridden / Dynamic / Reflection = Runtime