Kindle Previewer is a Java application, which seems to require JDK 1.6 and does not run on JDK 1.7.
To fix the environment, open
/Applications/Kindle Previewer.app/Contents/MacOS/Launcher and add JAVA_HOME pointing to your JDK 1.6 installation right after #!/bin/sh, e.g.
NEW workshop: Building HTML 5 Applications With Angular 2
Full week in December 2016: from Java EE 7 Bootstrap, Effective, Architectures over Testing to Microservices
On demand workshops: Java EE 7: Bootstrap, Effective, Testing and Microservices available for streaming.