如果我有一个使用通用类型的类，例如

public class Record<T> {
    private T value;

    public Record(T value) {
        this.value = value;
    }
}

如果我知道使用的所有类型（例如本例中的情况），那么在设计时就可以直接键入所有内容：

// I type explicitly
String myStr = "A";
Integer myInt = 1;
ArrayList myList = new ArrayList();

Record rec1 = new Record<String>(myStr);
Record rec2 = new Record<Integer>(myInt);
Record rec3 = new Record<ArrayList>(myList);

如果从“我不知道类型”的“某处”获得对象列表会怎样？如何分配类型：

// now let's assume that my values come from a list where I only know during runtime what type they have

ArrayList<Object> myObjectList = new ArrayList<Object>();
    myObjectList.add(myStr);
    myObjectList.add(myInt);
    myObjectList.add(myList);

    Object object = myObjectList.get(0);

    // this fails - how do I do that?
    new Record<object.getClass()>(object);