Design and Architectural Principles - Java 8 Lambdas - page 118

Figure 8-1. The command pattern

Let's look at a concrete example of the command pattern and see how it improves with
lambda expressions. Suppose we have a GUI Editor component that has actions upon it that
we'll be calling, such as open or save , like in Example 8-1 . We want to implement macro
functionality—that is, a series of operations that can be recorded and then run later as a
single operation. This is our receiver.

Example 8-1. Common functions a text editor may have
public public interface interface Editor Editor {

public public void void save ();

public public void void open ();

public public void void close ();

}

In this example, each of the operations, such as open and save , are commands. We need a
generic command interface to fit these different operations into. I'll call this interface Ac-
tion , as it represents performing a single action within our domain. This is the interface that
all our command objects implement ( Example 8-2 ).

Example 8-2. All our actions implement the Action interface
public public interface interface Action Action {

public public void void perform ();