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//Represents list books command for biblioteca
public class ListBooksCommand implements Command {
private static final String BOOKS = "Books::";
private static final String FORMAT = "%-35s %-35s %-35s";
private static final String HEADER = String.format(FORMAT, "Name", "Author", "YearPublished");
private static final String NO_BOOKS_AVAILABLE = "No Books Available";
private final Biblioteca biblioteca;
private final IO io;
public ListBooksCommand(Biblioteca biblioteca, IO io) {
this.biblioteca = biblioteca;
this.io = io;
}
@Override
public void execute() {
if (this.biblioteca.isEmpty(Book.class)) {
this.io.println(NO_BOOKS_AVAILABLE);
return;
}
this.displayBooks();
}
private void displayBooks() {
this.io.println(BOOKS);
this.io.println(HEADER);
this.io.println(this.biblioteca.representationOfAllLibraryItems(Book.class));
}
}
public class ListMoviesCommand implements Command {
private static final String Movies = "Movies::";
private static final String FORMAT = "%-35s %-35s %-35s";
private static final String HEADER = String.format(FORMAT, "Name", "Director", "YearPublished");
private static final String NO_BOOKS_AVAILABLE = "No Movies Available";
private final Biblioteca biblioteca;
private final IO io;
public ListBooksCommand(Biblioteca biblioteca, IO io) {
this.biblioteca = biblioteca;
this.io = io;
}
@Override
public void execute() {
if (this.biblioteca.isEmpty(Movie.class)) {
this.io.println(NO_MOVIES_AVAILABLE);
return;
}
this.displayMovies();
}
private void displayMovies() {
this.io.println(MOVIES);
this.io.println(HEADER);
this.io.println(this.biblioteca.representationOfAllLibraryItems(MOVIE.class));
}
}
我在這裏有兩個類，一個是listbooks命令，listmovies命令都在biblioteca上執行。 Book和Movie都是類型LibraryItem（接口）。 以下兩個代碼都是一樣的。兩者都會要求biblioteca獲得自己類型的代表性。這兩個命令都會顯示該表示。如何刪除重複？
這是藏書實現
//Represents a library
public class Biblioteca {
private final List<LibraryItem> allLibraryItems;
public String representationOfAllLibraryItems(Class<? extends LibraryItem> itemType) {
return this.allLibraryItems
.stream()
.filter(libraryItem -> libraryItem.getClass().equals(itemType))
.map(LibraryItem::representation)
.collect(Collectors.joining(LINE_SEPARATOR));
}
public boolean isEmpty(Class<? extends LibraryItem> itemType) {
return this.allLibraryItems.stream().noneMatch(libraryItem -> libraryItem.getClass().equals(itemType));
}
}
請建議我的模式，以避免重複。
這些類型的'執行命令'似乎是錯誤的。他們應該實現/擴展處理這種bookeping的父類型（例如'LibraryItem'抽象類 - 你已經提到這種類型已經存在）。如果存在任何這樣的項目，抽象類應該處理詢問「Biblioteca」，以便子類只關心它們如何顯示。 – dimo414
你的問題有點不清楚。你說的是，下面的代碼都是類似的。你在說什麼代碼？ –
這兩個listbooksCommand，ListMoviesCommand都有相同的代碼。 – Srinivas