The magic number at the start of all Java class files.

Every Java program compiled into bytecode must start with the hex (base 16) bytes CA, FE, BA, and BE to help identify it as a valid class file.

For those users that somehow need to know the value in decimal, but don't know hexadecimal*, here it is: 202, 254, 186, and 190.
* being too lazy to convert does not count as being a luser :)