Q:

To open "Eclipse" you need to install the legacy Java SE 6 runtime

Just installed a fresh version of Kepler 64bit "for Java Developers" on Yosemite, getting this error on first launch. Any thoughts on how to fix? Really do not want to downgrade my Java version!

A:

I just encountered this in another Eclipse-based app on Yosemite and figured out (with help from the references below) how to get the app running without installing the legacy Java SE 6 JRE. Here are the steps in case it helps other devs get Eclipse working.
PRECONDITIONS
$ sw_vers -productVersion 
10.10.1
$ java -version
java version "1.8.0_25"
Java(TM) SE Runtime Environment (build 1.8.0_25-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.25-b02, mixed mode)

Other configurations might work; this is my environment.
STEPS

Edit the info.plist for the JDK after installing:
$ sudo nano `/usr/libexec/java_home -V`/../info.plist

Change the following section:
<key>JVMCapabilities</key>
 <array>
  <string>CommandLine</string>
 </array> 

to 
<key>JVMCapabilities</key>
 <array>
  <string>JNI</string>
  <string>BundledApp</string>
  <string>WebStart</string>
  <string>Applets</string>
  <string>CommandLine</string>
 </array>

Try to open the app from the command-line (not sure if this is strictly necessary, but what I did)
You should get an error "(app) can't be opened because it is from an unidentified developer." 
Go to System Preferences: Security Settings (General) and you should see the recent app next to a button "Open Anyway" -- click this button to open the app.

This opens Eclipse without requiring the separate download of the legacy Java SE 6 files.
NOTES
When I was solving this on MTGBrowser (below) I also followed advice to change the info.plist of the app by adding the following section to the 'Eclipse' key:
<string>-vm</string><string>/Library/Java/JavaVirtualMachines/jdk1.8.0_25.jdk/Contents/Home/bin/java</string>

However, I'm not sure that's strictly required.  In any case, that wasn't sufficient -- I also had to change the JDK info.plist and security as described above for a complete solution.
REFERENCES

https://sourceforge.net/p/mtgbrowser/bugs/402/#c78c
http://crunchify.com/os-x-mavericks-eclipse-java-issue/
http://mac-how-to.wonderhowto.com/how-to/open-third-party-apps-from-unidentified-developers-mac-os-x-0158095/

A:

I was facing this trouble for hours. I followed every suggestion I could find over numerous forums with no success. I resolved the issue by simply installing 1.8.x JDK instead of the JRE, despite having no intension to develop for Java. I guess eclipse requires this.

A:

I ended up relenting and downloading Java 6 from here:
http://support.apple.com/kb/DL1572?viewlocale=en_US&locale=en_US
Apparently this seems to coexist ok with the latest Java version which I also installed (version 8 update 25) and version 8 shows up as the version I'm running when I verify from 
https://www.java.com/en/download/installed.jsp
I'm unclear on the security implications of this though, would have preferred another solution, if anyone finds a better solution than installing 6 please let me know.

