Eclipse How to fix java.lang.UnsupportedClassVersionError

For your problem you might wanna try to use other versions.
Some examples on what version you can use for your error:
45 = Java 1.1
46 = Java 1.2
47 = Java 1.3
48 = Java 1.4
49 = Java 5
50 = Java 6
51 = Java 7
52 = Java 8
53 = Java 9
54 = Java 10
55 = Java 11
56 = Java 12
57 = Java 13