Chapter1

Question 1

Name primitive types in relative order:

Answer 1

Boolean, byte(8bit), short, Int, long, float(32bit), double(64bit), char(16bit)

Question 2

long max = 312456789;

Does not compile. Why?

Answer 2

Needs ‘L’ on literal.

long max = 312456789L;

Question 3

int i1, i2, i3 = 0;

How many declared?
How many initialized?

Answer 3

3 declared.

1 initialized.

Question 4

Three rules for legal identifiers:

Answer 4

Must begin with letter, $ or _.
Subsequent characters may be numbers.
No reserved words (although different case technically allowed)

Question 5

Local, instance and class variables? Difference between?

Answer 5

Local is in a method.
Instance is a field in a class.
Class variable shared across multiple objects using static.

Question 6

Defaults for Boolean, byte, Int, float, double, char, objects

Answer 6

False, byte:0, Int:0, float:0.0, double:0.0, char:’\u0000’, object:null

Question 7

Order of initialisation?

Answer 7

Fields and instance blocks run in order in which they appear. Then constructor runs.

Question 8

A byte can God a value from …?

Answer 8

-128 to 127. A byte is 8 bits. A bit has two possible values. So 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 = 256. 0 needs to be included.

Question 9

Name 3 other base numbers Java recognizes:

Answer 9

Octal 017
Hexadecimal 0xFf
Binary 0b10

Question 10

Which are valid?
boolean b1, b2;
String s1 = "1", s2;
double d1, double d2;
Int i1; int i2;
int i3; i4;

Answer 10

Legal
Legal
Not legal
Legal
Not legal

Question 11

Order of elements in a class… ie methods, import statements etc

Answer 11

Package declaration, import statements, class declaration, field and methods.
Only class declaration is required

Question 12

How many classes can there be in a file? Other rules?

Answer 12

Multiple. But only one must be public. Both can be not public. Also one must be named after file.

Question 13

Rules about garbage collection?

Answer 13

Calling System.gc doesn’t guarantee garbage collection. An object remains on heap until it is no longer reachable: no references or all references gone out of scope.

Question 14

finalize()?

Answer 14

Gets called if the garbage collector tries to collect object. Can run zero or one time.

Question 15

Java is an interpreted language, it gets compiled to…

Answer 15

bytecode (a .class file). The same class files run everywhere.

Question 16

Java is robust, why?

Answer 16

Manage memory on it’s own, automatic garbage collection, prevents memory leaks. C++ doesn’t.

Question 17

Java code runs inside…

Answer 17

The JVM. Makes it safe so code doesn’t do bad things to computer.

Question 18

Which variables must be initialized before use?

Answer 18

Local variables must be initialized. Instance an class do not need o e initialized.

Question 19

Does Java have operator overloading and pointers?

Answer 19

No.

Question 20

Is Java a functional programming language?

Answer 20

No. Object oriented.