I want to know the use of netweaver in java application as compare to other IDE's.
You can say like this "Use of Java Application in the NetWeaver.
The java application helps to develop various conepts of NetWeaver like Portals,Web dynpro,Web Services etc.
The java application works using the various servers like J2EE and WebSphere.
I dont know any other ides which is using Java application.
I hope this will help to clear your doubts.
I guess you mean the NetWeaver Developer Studio (NWDS) - which is the IDE - and not the NetWeaver Platform. The NWDS gives you access to the Java Development Infrastructure allowing to manage the lifecycle & delivery of applications, supports SAP specific project types like Web Dynpro, Portal Development, Mobile Applications, Dictionary aso.
Like other IDEs it offers support development and deployment of J2EE-applications (EJB, Web), but only works with SAPs J2EE-engine.
To be honest I don' t think there' s a reasonable comparison to other IDEs possible. You get more information from the development manual on help.sap.com.