meenal deshpande wrote:What are the significance of java IdEs...
IDEs are great for writing code especially production code.
You do not need to use an IDE, but they do tend to make things easier as they offer things like spell checking, syntax highlighting, debugging and more.
However you can use something like Windows Notepad to program Java (and many other languages) in.
meenal deshpande wrote:...and which is the best IDE
This depends on who you ask and what the purpose is. Everyone will have their own "best".
If you are more interested in Android programming then you may be more interested in Kotlin and as a result you would probably gravitate towards IntelliJ.
A rebranded version of IntelliJ is provided for free by Google and JetBrains for Android development. JetBrains are the ones who started the Kotlin language.
In the end @meenal, you will probably find that most Java IDEs have close to the same functionality especially if you extend them with plugins/addons.
So the question then becomes which IDE do you like to use and why?
Some companies may enforce and IDE and others may not.
Two of the most popular IDEs for Java are Eclipse and IntelliJ and it can be helpful to know how to use both of them.