How can you implement a method call that exists in an external library?

To call a method from an external library in Java, you need to:

1. Add the library to your project (for example, via Maven, Gradle, or manually adding a JAR file).
2. Import the required class from the library.
3. Create an object of that class (if the method is not static) or call the static method directly.

Example:

// Import class from external library
import com.example.lib.ExternalClass;

public class Main {
    public static void main(String[] args) {
        // Create an object
        ExternalClass obj = new ExternalClass();
        // Call the method
        obj.externalMethod();

        // Or call a static method
        ExternalClass.staticMethod();
    }
}

It is important to ensure that the library is correctly linked to the project, otherwise the compiler will not be able to find the classes.