byte (8bits)
short (16bits)
int (32bits)
long (64bits)
float (32bits)
double (64 bits)
A defult value of primitive is 0.
You can put a suffix to double and float, like 1.5d or 1.5f.
boolean / char
boolean --> true or false
char --> character (16bits), defaut \u0000
String
String is an immutable object; actually String is a Java class.
There are a couple of ways to create a String instance.
String str = "Hello world";
String str = new String ("Hello world");
exapmple
String s1 = "Hello";
String s2 = s1;
then s2 and s1 refer to the same "Hello" in the pool.
"Hello" is a String object and s1 refers to the object.
In other words, variables (except primitives) are objects, each of which referes to an instance.
