C has no class types
C variables can be used even though not initialized
C has pointer types and operators on pointers.
C can allocate new memory with library function 'malloc', specifying a number of bytes, not a data type; Java allocates new memory with the new operator yielding an instance of some data type
C has no garbage collector; memory allocated with malloc, must be explicitly released with the library function 'free'.
C function declarations can be separate from the implementations

Some C and Java differences