Newlines

Always use the language-specific alternative to a platform-specific newline.

REASONING: Some platforms use \n, some use \r\n. Hardcoding these values into your program could cause some compatibility issues with other platforms.

C++

Using std::endl or \n. std::cout will correctly format \n to the correct platform newline character. It is recommended to still use std::endl. HOWEVER, std::endl will flush the ostream, so if you want to avoid that, use a plain \n (not \r\n)

Java

Use System.lineSeperator()

BAD:

System.out.println("Hello!\n");

GOOD:

System.out.println("Hello!" + System.lineSeparator());