Setting up and using different data structures in Java
// The `char` data type is used to represent single characters. That includes the keys on a keyboard that are used to produce text.
// `char` is short for character and can represent a single character.
// All char values must be enclosed in single quotes, like this: 'G'.
// In Java, all VARIABLES must have a specified data type.
int myNumber = 42;
boolean isFun = true;
char movieRating = 'A';
// Equality OPERATORS do not require that operands share the same ordering.
// You can test equality across boolean, char, or int data types.
// Creating and initializing an ArrayList
// The `add` method will insert at the first position (0) into the list.
ArrayList<String> olympicSports = new ArrayList<String>();
olympicSports.add("Archery");
olympicSports.add("Boxing");
// iterating through an array
for (String sport: olympicSports) {
System.out.println(sport);
}
// Creating an initializing a hash map
// below we create a HashMap object called myFriends
// stores keys of type `String` and values of type `Integer`
HashMap<String, Integer> myFriends = new HashMap<String, Integer>();
// new method calls object name, but with '()'
`new HashMap<String, Integer>();`
// add to
myFriends.put("Beijing", 28);
myFriends.put("London", 29);
myFriends.put("Rio de Janeiro", 22);
// length (in this case, 3)
myFriends.size();
for (int i = 0; i < quizGrades.size(); i++) {
System.out.println( quizGrades.get(i) );
}
// foreach loop
// the colon (:) can be read as "in"
for (Integer grade : quizGrades){
System.out.println(grade);
}