How do delegates work at compile time in Java…

Delegates in Java are not a native language construct like in C#. Their functionality is emulated using existing mechanisms. At the compile level, this is usually implemented through:

Interfaces: Define a contract (a set of methods) that must be implemented.

// Example interface
interface MyDelegateInterface {
    void doSomething(String data);
}

Implementation classes: A class implementing the interface acts as the object to which the call is delegated.

// Class implementing the interface
class MyDelegateImpl implements MyDelegateInterface {
    @Override
    public void doSomething(String data) {
        System.out.println("Delegated action with data: " + data);
    }
}

A class containing the "delegate": This class holds a reference to an object implementing the interface and calls its methods.

// Class using the "delegate"
class Delegator {
    private MyDelegateInterface delegate; // Reference to delegate object

    public Delegator(MyDelegateInterface delegate) {
        this.delegate = delegate;
    }

    public void performDelegatedAction(String data) {
        // Delegating the call
        delegate.doSomething(data);
    }
}

During compilation, Java code is translated into bytecode (.class files). In bytecode, method calls on the delegate object (delegate.doSomething(data);) become regular method calls of the virtual machine (e.g., invokevirtual or invokeinterface), working with the specific implementation of the interface that the delegate variable references at runtime.

In other words, the Java compiler does not recognize a special concept of "delegate". It simply works with interfaces, classes, objects, and references as with ordinary language elements. The delegation mechanism is implemented at the object-oriented design level, and the compiler treats it as standard method calls through object references.

How do delegates work at compile time in Java?