Language Fundamentals

How many number of non-public class definitions can a source file have
A source file can contain unlimited number of non-public class definitions
List primitive data types, there size and there range (min, max)

DataType  Bytes  bits  min   max
boolean    -      1     -     -
char       2     16     0   2^16-1
byte       1      8   -2^7  2^7-1
short      2     16   -2^15 2^15-1
int        4     32   -2^31 2^31-1
long       8     64   -2^63 2^63-1
float      4     32     -    -
double     8     64     -    -

What types of values does boolean variables take
It only takes values true and false
Which primitive datatypes are signed
All except char and Boolean
Is char type signed or unsigned
char type is integral but unsigned. It range is 0 to 2^7-1
What forms an integral literal can be
decimal, octal and hexadecimal, hence example it can be 28, 034 and 0x1c respectively
What is the default value of boolean
False
Why is the main method static
So that it can be invoked without creating an instance of that class
What is the difference between class variable, member variable and automatic(local) variable
class variable is a static variable and does not belong to instance of class but rather shared across all the instancesmember variable belongs to a particular instance of class and can be called from any method of the classautomatic or local variable is created on entry to a method and has only method scope
When are static and non static variables of the class initialized
The static variables are initialized when the class is loadedNon static variables are initialized just before the constructor is called
When are automatic variable initialized
Automatic variable have to be initialized explicitly
How is an argument passed in java, by copy or by reference
If the variable is primitive datatype then it is passed by copy.If the variable is an object then it is passed by reference
What is garbage collection
The runtime system keeps track of the memory that is allocated and is able to determine whether that memory is still useable. This work is usually done in background by a low-priority thread that is referred to as garbage collector. When the gc finds memory that is no longer accessible from any live thread it takes steps to release it back to the heap for reuse
Does System.gc and Runtime.gc() guarantee garbage collection
No