How do I know if I have JRE or JDK installed?

Related questions

1. How does the JRE work?
2. Is JRE platform independent?
3. Why is JVM needed?
4. Can JRE run Java program?
5. What JRE in Java?
6. Do I need both JRE and JDK?
7. Is Java JRE free for commercial use?
8. Do we need JRE to run Java?
9. Does Eclipse include JDK?
10. Does Eclipse Need a JDK?

Tags

1. #version
2. #features
3. #installed
4. #listed
5. #there
6. #program
7. #variables
8. #start
9. #command
10. #advanced
11. #control
12. #check
13. #prompt
14. #panel
15. #system
16. #correctly
17. #environment