What does the error T does not match T mean in my Java code?

In summary, The conversation is about a compilation error that the person is getting in their code and they are not able to understand it. They share the code segment where the error is occurring and ask for help in understanding it. The person responding advises them to copy the error message and mention the line number for better understanding and help.
  • #1
magnifik
360
0
I am getting compilation errors in the following segment of my code:

_underlyingStorage was declared in the following way: private T[] _underlyingStorage = (T[]) new Object[128];

public T next() {
_currentIndex++;
if(_underlyingStorage[_currentIndex] == _underlyingStorage[_numElements-1])
_underlyingStorage[_currentIndex] = _underlyingStorage[0];
return _underlyingStorage[_currentIndex];
}

the error I'm getting makes no sense to me.. it says that T does not match T. what's happening here?
 
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  • #2
Where are you getting the error at? I entered everything you had into a class, but I'm not getting any error.
 
  • #3
magnifik said:
the error I'm getting makes no sense to me.. it says that T does not match T. what's happening here?
Errors reported by the compiler and the runtime are usually very precisely worded, containing a very literal description of a problem in your program and where that problem occurs.

If you aren't yet experienced enough to extract this information from an error, you should copy it verbatim when you ask for others to help. (also, there's probably a line number involved. It would help if you point out which line of your code it refers to)
 
1.

What is a Java generic array list?

A Java generic array list is a data structure that allows for the storage and manipulation of a collection of objects of the same type. It is similar to a regular array, but with added functionality such as dynamic resizing and built-in methods for adding, removing, and accessing elements.

2.

How do you declare a Java generic array list?

To declare a Java generic array list, you must first import the necessary package: import java.util.ArrayList; Then, you can declare the array list variable using the following syntax: ArrayList<DataType> listName = new ArrayList<>(); Make sure to replace DataType with the type of objects you want to store in the array list.

3.

What are the benefits of using a Java generic array list?

There are several benefits of using a Java generic array list, including:

  • Dynamic resizing: Unlike regular arrays, a generic array list can automatically resize itself to accommodate new elements.
  • Type safety: The use of generics ensures that only objects of the specified type can be added to the array list.
  • Built-in methods: The array list class provides built-in methods for common operations such as adding, removing, and accessing elements.
  • Easy iteration: The use of for-each loops makes it easy to iterate through the elements in an array list.
4.

Can a Java generic array list hold primitive data types?

No, a Java generic array list can only hold objects. If you want to store primitive data types, you can use the corresponding wrapper classes (e.g. Integer for int, Double for double, etc.) or consider using a regular array instead.

5.

How do you add and remove elements from a Java generic array list?

To add elements to a Java generic array list, you can use the add() method, passing in the object you want to add as the parameter. To remove elements, you can use the remove() method, passing in either the index of the element or the object itself as the parameter. Both methods will return a boolean value indicating whether the operation was successful or not.

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