Your current Java version is greater than 6 and you get after starting PyCharm an error dialog, the following solution helps.

Check your Java Version

# show Java version
$ 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)

Open PyCharm settings

# edit file with Vim
$ vim /Applications/PyCharm\ CE.app/Contents/Info.plist

Change following lines on XML

<key>JVMVersion</key>
<string>1.6*</string>

# change into
<key>JVMVersion</key>
<string>1.8*</string>

Now you can start PyCharm