如何检查正在使用的数据类型？

Question

I have an assignment in which one of the methods of class creates a tree node of generic type T.

Answer 1

For any TreeNode object treeNode ,

treeNode.getData() instanceof LinkedList

will return true if the dataItem is an instance of LinkedList. Same goes for CircularArray.

Answer 2

To test if an object reference is an instace of a specific class there is the infix operatorinstanceof . You can use that in an if-else-statement to handle the three different cases.

Object data = treeNode.getData();
if (data instanceof LinkedList) {
    LinkedList list = (LinkedList)data;
    // do stuff ...
} else if (data instanceof CircularArray) {
    CircularArray array = (CircularArray)data;
} else {
    // error state - throw excpetion or handel this case someother way
}