我正在嘗試創建一個助手。我的應用程序可以有許多庫，一旦實例化，我想創建一個工廠以便能夠跨類共享實例，即：public ArrayList<Helper> helper = new ArrayList<>(asList( new Helper(SomeLib.class, new SomeLib()), new Helper(SomeOtherLib.class, new SomeOtherLib())));我的圖書館課程目前是測試這項工作的標準。class Library { public Library() { System.out.println("Instance is working"); }}我試圖開始工作的示例庫如下所示：public class ExampleLib extends Library { public void test() { System.out.println("Test OK"); }}我當前的 Helper 類看起來像這樣，但是，我無法將庫強制轉換回原來的繼承類，我嘗試了多種方法：import dreambot.libs.Library;public class Helper { private Library lib; private Class<? extends Library> name; public Helper(Class<? extends Library> name, Library lib) { this.name = name; this.lib = lib; } public Class<? extends Library> getName() { return name; } public <Library> Library getLib() { // All the things I've tried to do return (this.name) lib; return name.cast(lib); return lib.getClass().cast(lib); }}反過來，我想要的是：public ArrayList<Helper> helper = new ArrayList<>(asList( new Helper(ExampleLib.class, new ExampleLib()),));public void test() { Arrays.stream(helper.toArray()).filter(c -> c.getName(ExampleLib.class)).getFirst().ifPresent(h -> { h.getLib().test(); // Should output "Test OK" });我在 IDE 中收到的錯誤Helper::getLib是：不是一個聲明return (this.name) lib;需要不兼容的類型：庫，找到：dreambot.libs.Library for return lib.getClass().cast(lib);和return name.cast(lib);任何幫助，將不勝感激。
1 回答
墨色風雨
TA貢獻1853條經驗 獲得超6個贊
嘗試：
import dreambot.libs.Library;
public class Helper<T extends Library> {
private T lib;
private Class<T> name;
public Helper(Class<T> name, Library lib) {
this.name = name;
this.lib = lib;
}
public Class<T> getName() { return name; }
public T getLib() {
return lib;
}
}
甚至更簡單：
import dreambot.libs.Library;
public class Helper<T extends Library> {
private T lib;
public Helper(Library lib) {
this.lib = lib;
}
public Class<T> getName() { return lib.getClass(); }
public T getLib() {
return lib;
}
}
并且在調用構造函數時不要忘記鉆石運算符：
public ArrayList<Helper> helper = new ArrayList<>(asList(
new Helper<>(SomeLib.class, new SomeLib()),
new Helper<>(SomeOtherLib.class, new SomeOtherLib())
));
可以簡化為：
public ArrayList<Helper> helper = new ArrayList<>(asList(
new Helper<>(new SomeLib()),
new Helper<>(new SomeOtherLib())
));
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