invokevirtual

INVOKEVIRTUAL is an instruction in the Java Virtual Machine (JVM) bytecode. It is used to invoke an instance method on an object. The JVM determines at runtime which specific method implementation to execute based on the actual class of the object, rather than the declared type of the variable. This dynamic dispatch mechanism is a core feature of object-oriented programming and is fundamental to polymorphism in Java.

When the JVM encounters an INVOKEVIRTUAL instruction, it looks at the object reference on the operand stack. It then examines the class of that object and searches for the appropriate method to execute, taking into account inheritance and method overriding. If the method is found in the object's class or any of its superclasses, that implementation is invoked. This process ensures that the correct behavior is executed even when working with objects of different subclasses through a common superclass reference.

INVOKEVIRTUAL is distinct from instructions like INVOKESTATIC (for static methods) and INVOKESPECIAL (for constructors, private methods, and superclass methods). The runtime nature of INVOKEVIRTUAL makes it a powerful tool for flexible and extensible code design, allowing developers to write code that can adapt to different object types without explicit type checking.