Adds new line marker to text that is actually in StringBuffer. Next part will be shown in the line below.

+ creates new intermediate String objects as Strings are immutable in Java whereas StringBuffer's append() works on the same string and that's why it is considered faster. However, you should use StringBuilder from java 5 onwards as it is said to be faster than StringBuffer as its methods are not synchronized like StringBuffer.

This is high level theoritical explanation. For more specific details look at String concatenation: concat() vs "+" operator post.

Nope.

And given that they're hardcoded strings, it'd be identical to write

buff1 = new StringBuffer("some value Asome value B");

BTW, it's a bit more efficient to use a StringBuilder rather than a StringBuffer (and the API is identical).

Thanks to the compiler, you are already using StringBuilder which is the newer, faster version of StringBuffer.

Your code above will compile to the equivalent of:

public static void winner ()
{
  if (position1 >= 100){
    System.out.println(new StringBuilder("THE WINNER IS ").append(name1).toString()); 
  }
  else if (position2 >= 100){
    System.out.println(new StringBuilder("THE WINNER IS ").append(name2).toString()); 
  }
}

So, in this case, you would not be accomplishing anything that isn't already being done for you. Use StringBuilder when you are building a String in a loop.

In your situation, they were probably talking about pre-initializing a single StringBuilder for both cases:

public static void winner() {
  StringBuilder out = new StringBuilder("THE WINNER IS ");
  if (position1 >= 100) {
    out.append(name1);
  } else if (position2 >= 100 {
    out.append(name2);
  } else {
    return; // Preserve previous behavior just in case, remove this if it's not needed
  }
  System.out.println(out);
}