CHAPTER 9
SECTION 6
"StringBuffer"

- String object is immutable (once created, can't be changed)
  - cannot add, delete, or modify characters
  - a String class method does not change a String, it returns a new method reflecting the change
  - maintains an efficient memory allocation scheme for managing String objects
  - lets us treat Strings as primitives
- String manipulation: operations such as replacing a character, appending a string with another string, deleting a portion of a string, etc.
  - performed via the StringBuffer class
- StringBuffer
  - objects must be created using the reserved word new
  - cannot directly assign a String to an object of type StringBuffer
  - constructor takes a single String argument
  - setCharAt method
    - first argument
      - int
      - for the character position
    - second argument
      - char
      - new value of that position
  - append method
    - argument
      - any primitive type
    - concatenates the argument to the String represented by the StringBuffer
    - Java compiler may implicitly use StringBuffer when compiling string concatenation
      - using the append StringBuffer method is better than using string concatenation because it avoids creating temporary string objects
  - insert method
    - first argument: int index where insertion begins
    - second argument: string to insert

Quick Check
1. a. "Dr. Caffeine"
   b. "Deaffe"
   c. "Deeinfe"
2. StringBuffer sb = new StringBuffer(str);
   char curChar;
   for (int i = 0; i < str.length(); i++) {
       curChar = sb.charAt(i);
       if (curChar == 'a' || curChar == 'e' || curChar == 'i' || curChar == 'o' || curChar == 'u') {
           sb.setCharAt(i, 'C');
       }
   }
  
3. line 2: can't assign a String to a StringBuffer directly
   line 4: must use System.out.println
           can't directly output a StringBuffer
   line 5: can't concatenate a String and a StringBuffer
   line 5: must convert the right-hand-side to a StringBuffer to perform the assignment