将T作为参数传递给Java，有条件地创建Generic(Pass T as a parameter to to conditionally create Generic in Java)

将T作为参数传递给Java，有条件地创建Generic(Pass T as a parameter to to conditionally create Generic in Java)

我试图在Java中有条件地创建一个Generic实例，其中类型作为参数传递。 像这样的东西：

private void doStuff(somethingThatDescribesWhatTShouldBeHere) { ArrayList<thetypeTthatwaspassedin> = new ArrayList<thetypeTthatwaspassedin> ... rest of logic }

我无法弄清楚我的生活，如果没有ArrayList<T>回应我，T参数应该是什么样子。

我们的想法是，如果T是一个字符串，那么ArrayList<String>就会被实例化。如果它是Foo，那么ArrayList<Foo>会在内部实例化。

请帮忙

I am trying to conditionally create a Generic instance in Java where the type is passed as a parameter. Something like this:

private void doStuff(somethingThatDescribesWhatTShouldBeHere) { ArrayList<thetypeTthatwaspassedin> = new ArrayList<thetypeTthatwaspassedin> ... rest of logic }

I cannot figure out for the life of me what the T parameter should look like without the ArrayList<T> screaming back to me.

The idea is if T is a string then an ArrayList<String> is instantiated .. if it is Foo then an ArrayList<Foo> is instantiated instead inside.

Please help

最满意答案

好吧，只需使doStuff泛型：

// If you can, pass a parameter of type T : private <T> void doStuff(T something) { ArrayList<T> = new ArrayList<T>(); ... rest of logic } // so it can be called like that : YourType param = ...; foo.doStuff(param); // If you can't pass a parameter of type T, you'll have // to explicitly tell the compiler which type to use : foo.<YourType>doStuff();

如Stijn Geukens暗示的那样传递Class<T>也是一种避免丑陋的后一种语法的常用方法，如果你不需要传递一个实际的对象。

Well, just make doStuff generic :

// If you can, pass a parameter of type T : private <T> void doStuff(T something) { ArrayList<T> = new ArrayList<T>(); ... rest of logic } // so it can be called like that : YourType param = ...; foo.doStuff(param); // If you can't pass a parameter of type T, you'll have // to explicitly tell the compiler which type to use : foo.<YourType>doStuff();

Passing Class<T> as hinted by Stijn Geukens is also a common way of avoiding the ugly, latter syntax if you don't need to pass an actual object.