I used the Learn Java modules from Codeacademy to refresh my Java knowledge.
Notes:
The precedence of each Boolean operator is as follows:
!
is evaluated first&&
is evaluated second||
is evaluated third
ternary conditional statement:
char canDrive = (fuelLevel > 0) ? ‘Y’ : ‘N’;
Switch
int subwayTrain = 5;
switch (subwayTrain){
case 1 : System.out.println(“This is a South Ferry bound train!”);
break;
case 5 : System.out.println(“This is a Brooklyn bound train!”);
break;
case 7 : System.out.println(“This is a Queens bound train!”);
break;
default:
System.out.println(“I’m not sure where that train goes…”);
}
By the way, I found switch statement very powerful combined with finite state machine (FSM) when doing my Arduino course projects.
Object Oriented Programming
structure:
class Name extends AnotherClass{
instance variable
constructor (parameters)
method (void, or has return value)
main{
create new object;
call method;
}
}
ArrayList
Declare an ArrayList object storing integers:
ArrayList<Integer> listName = new ArrayList<Integer>();
Add 3 to the list:
listName.add(3);
Get a value at index 0:
listName. get(0);
Insert a new value 22 to index 2:
listName.add(2,22);
the size of list:
int size = listName.size();
for each loop:
for (Integer value : listName){
}
HashMap
Declare a HashMap object (store String keys and Integer values):
HashMap<String, Integer> name = new HashMap<String, Integer>();
the size of HashMap:
int size = name.size();
Add keys and values:
name.put(“key”, 1);
Get value using key:
name.get(“key”);
for each loop:
for (String item: name.keySet()) {
}