如何创建通用数组？ [英] How to create generic array?

问题描述

可能重复：

Java如何：通用数组创建

如何在Java中创建类型为 T [] 的数组？我无法使用 Arrays.newInstance（），因为我没有 Class< T> 的对象。在某个地方有 newInstance 的通用版本吗？

How to create an array of type T[] in Java? I can't use Arrays.newInstance() since I have no objects of Class<T>. Is there a generic version of newInstance somewhere?

我的方法原型如下：

public <T> T[][] distribute(T ... balls) {
   T[][] answer = ????

   // filling answer with data

   return answer;

}

更新

抱歉，在上面的示例中，我可以从球上课。但假设我没有这样的变量。

Sorry in example above I can take class from balls. But suppose I have no such a variable.

public <T> T[][] distribute() {
   T[][] answer = ????

   // filling answer with data

   return answer;

}

或

class<T> {
   public T[][] distribute() {

      T[][] answer = ????

      // filling answer with data

      return answer;

   }
}

UPDATE2

此示例也不起作用：

public abstract class GenericArray<T> {

abstract public T create();

public T[] gen1() {
    T[] ans = (T[]) new Object[3];
    ans[0] = create();
    ans[1] = create();
    ans[2] = create();
    return ans;
}

public Integer[] gen2() {
    Integer[] ans = new Integer[3];
    ans[0] = new Integer(0);
    ans[1] = new Integer(0);
    ans[2] = new Integer(0);
    return ans;
}

public static void main(String[] args) {

    GenericArray<Integer> a = new GenericArray<Integer>() {

        @Override
        public Integer create() {
            return new Integer(0);
        }
    };

    Integer[] b = a.gen2();
    Integer[] c = a.gen1(); // this causes ClassCastException

    System.out.println("done");

}

}

推荐答案

1。。数组是不是 $ c>

1. Arrays are Not Generic

2。。这就是在检查过程中检查了数组的原因编译以及运行时，其中集合可以通用，并且仅在编译时进行检查 > ....

2. Thats the reason Arrays are checked during compile as well as runtime, where as Collections can be Generic and its checked only during the compile time....

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