What is the difference between Iterator and Listiterator ?

There are two Differences are there :

1. We can use Iterator to traverse Set and List and also Map type of Objects. But List Iterator can be used to traverse for List type Objects, but not for Set type of Objects.

That is, we can get a Iterrator object by using Set and List, see here :

 By using Iterator we can retrieve the elements from Collection Object in forward direction only.

Methods in Iterator :

1. hashNext()
2. next()
3. remove()

Iterator ite = Set.iterator();
Iterator ite = List.iterator();

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What is the difference between doGet() and doPost() methods ?

The difference has given below......

 

doGet	doPost
In doGet Method the parameters are appended to the URL and sent along with header information	In doPost parameters are sent in separate line in the body
Maximum size of data that can be sent using doget is 240 bytes	There is no maximum size for data
Parameters are not encrypted	Parameters are encrypted
DoGet method generally is used to query or to get some information from the server	DoPost is slower compared to doGet since doPost does not write the content length
DoGet should be idempotent. i.e. doget should be able to be repeated safely many times	This method does not need to be idempotent. Operations requested through POST can have side effects for which the user can be held accountable for example updating stored data or buying items online.
DoGet should be safe without any side effects for which user is held responsible.	This method does not need to be either safe.

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