What do u mean by wrapper Class? What do u mean by Jvm... How do u change JVM for other OS?

In general in java language everything is object but Primitive data types are not objects.We need a conversion
from primitive data type to object .For this conversion java provides Wrapper classes.
datatype Wrapper class
int-------Integer
float-----Float
double----Double
long------Long
short-----Short
byte------Byte
char------Char