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The diagram emphasizes events that cross the system boundary from actors to systems. A system sequence diagram should be done for the main success scenario of the use case, and frequent or complex alternative scenarios. There are two kinds of sequence diagrams: Sequence Diagram (SD): A regular version of sequence diagram describes how the ...
If-then-else flow diagram A nested if–then–else flow diagram. In computer science, conditionals (that is, conditional statements, conditional expressions and conditional constructs) are programming language constructs that perform different computations or actions or return different values depending on the value of a Boolean expression, called a condition.
Below is an example written in Java that takes keyboard input and handles each input line as an event. When a string is supplied from System.in , the method notifyObservers() is then called in order to notify all observers of the event's occurrence, in the form of an invocation of their update methods.
The UML sequence diagram shows the run-time interactions: In this example, the Sender object calls handleRequest() on the receiver1 object (of type Handler). The receiver1 forwards the request to receiver2, which in turn forwards the request to receiver3, which handles (performs) the request.
The bridge pattern is often confused with the adapter pattern, and is often implemented using the object adapter pattern; e.g., in the Java code below. Variant: The implementation can be decoupled even more by deferring the presence of the implementation to the point where the abstraction is utilized.
In the following example, a Mediator object controls the values of several Storage objects, forcing the user code to access the stored values through the mediator. When a storage object wants to emit an event indicating that its value has changed, it also goes back to the mediator object (via the method notifyObservers ) that controls the list ...
In the previous example, the class Component is inherited by both the ConcreteComponent and the subclasses that descend from Decorator. The decorator pattern is an alternative to subclassing . Subclassing adds behavior at compile time , and the change affects all instances of the original class; decorating can provide new behavior at run-time ...
A sample UML class and sequence diagram for the Command design pattern. [3]In the above UML class diagram, the Invoker class doesn't implement a request directly. Instead, Invoker refers to the Command interface to perform a request (command.execute()), which makes the Invoker independent of how the request is performed.