sql notes

- The only difference between UNIQUE and PRIMARY KEY is that the former allows null values while the latter doesn't.

inner classes in java

Java bytecode has no concept of an inner class, so the compiler translates the inner class into an ordinary class that can be accessed by any class in the current package. Since inner classes are supposed to have full access, any fields that the inner class accesses in the container class that are marked private, are silently changed to protected. This is baaaad.

I don’t really understand why, but this can be corrected by making the inner class private.

the life of a translated program (in a nutshell)

The compiler takes in source code and outputs assembly code.

The assembler takes in assembly code and outputs object code.

The linker takes one or more object code files, links them together, and outputs binary code.

The loader loads binary code into memory and it gets executed.