JM 5

Question 1

What is a Javadoc comment?

Answer 1

A Javadoc comment is set off from code by standard multi-line comment tags /* and */. The opening tag (called begin-comment delimiter), has an extra asterisk, as in /**. The first paragraph is a description of the method documented. Following the description are a varying number of descriptive tags, signifying: The parameters of the method (@param) What the method returns (@return) Any exceptions the method may throw (@throws) Other less-common tags such as @see (a “see also” tag)

Question 2

Name 3 good uses for comments

Answer 2

1. Explaining what a program does
2. Explaining obscure lines of code
3. Documenting the methods and classes that other programmers will use.
4. Disable parts of code e.g “commenting out” lines.

Question 3

Style vs Syntax?

A program begins with a comment.

Answer 3

Style

Question 4

Style vs Syntax

Names of all methods begin with a lowercase letter

Answer 4

Style

Question 5

Style vs Syntax

Each opening brace has a matching closing brace

Answer 5

Syntax

Question 6

Style vs Syntax

All statements within a pair of matching braces are indented by 2 spances.

Answer 6

Style

Question 7

Style vs Syntax

A closing brace is place on a separate line.

Answer 7

Style

Question 8

Style vs Syntax

A class has a lank line before each method declaration.

Answer 8

Style

Question 9

Style vs Syntax

The word IF is not used as a name for a variable.

Answer 9

Style

Question 10

What are the Java primitive data types?

Answer 10

1. char
2. byte
3. int
4. long
5. short
6. double
7. float
8. boolean
9. void
10. enum

Question 11

What are the java buil in constants?

Answer 11

1. true
2. false
3. null

Question 12

What are Java’s built-in storage/access modifiers?

Answer 12

1. public
2. private
3. protected

above are access modifiers

1. final
2. static

Question 13

What are Java’s built-in control statements (/keywords are used in control statements) ?

Answer 13

1. if
2. else
3. for
4. while
5. do
6. switch
7. case
8. default
9. break
10. return

Question 14

Which Java keywords deal with classses and inheritance?

Answer 14

1. import
2. class
3. interface
4. extends
5. implements
6. new
7. this
8. super
9. abstract
10. instanceof

Question 15

Which reserved words deal with exception handling?

Answer 15

1. try
2. catch
3. finally
4. throw
5. throws

Question 16

Other Java reserved words?

Answer 16

1. continue
2. package
3. native
4. volatile
5. transient
6. synchronized
7. assert
8. strictfp

Question 17

What are the components of a Java class?

Answer 17

The inner part of the class is where we define the fields, constructors, and methods that
give the objects of that class their own particular characteristics and behavior. We can
summarize the essential features of those three components of a class as follows:

1. The fields store data for each object to use.
2. The constructors allow each object to be set up properly when it is first created.
3. The methods implement the behavior of the objects.

In Java there are very few rules about the order in which you

Question 18

What are the access modifying keywords in Java?

Answer 18

1. public
2. private
3. protected

Question 19

Let us say you write a class without using the keyword public. Example:

class Foobar {

 .....

}

What restrictions come into play? Why did Gosling make Java so verbose, anyway? Python doesn’t have this public private nonsense and it seems to work OK?

Answer 19

A class may be declared with the modifier public, in which case that class is visible to all classes everywhere. If a class has no modifier (the default, also known as package-private), it is visible only within its own package (packages are named groups of related classes)

  At the member level, you can also use the public modifier or no modifier (package-private) just as with top-level classes, and with the same meaning. For members, there are two additional access modifiers: private and protected. The private modifier specifies that the member can only be accessed in its own class. The protected modifier specifies that the member can only be accessed within its own package (as with package-private) and, in addition, by a subclass of its class in another package.

Question 20

How can you identify a constructor of a class?

Answer 20

1. It has the same name as the class.

Question 21

Does a constructor have to have a return?

Answer 21

No. Constructors usually do not have returns. I don’t know if this is syntactically enforced. We should try it out.

Question 22

What is the difference between an instance variable and a field?

Answer 22

They mean the same thing – object oriented programming has a lot of confusing, vague terminology which often resolve to simple things. Look at this nice example:

http://www.bluej.org/objects-first/chapters/objects-first-ch2.pdf

Question 23

What is the meaning of the //, /*, and */ character sequences in the code?

Answer 23

They denote comments, which are ignored by the compiler. A comment is either
text in between /* and */ or at the end of a line after //.

Question 24

Q. What are Java’s rules regarding tabs, spaces, and newline characters?

Answer 24

A. Such characters are known as whitespace characters. Java compilers consider all whitespace in program text to be equivalent. For example, we could write Hel-loWorld as follows:
public class HelloWorld { public static void main ( String [] 
args) { System.out.print("Hello, World") ; System.out.
println() ;} }
But we do normally adhere to spacing and indenting conventions when we write 
Java programs, just as we always indent paragraphs and lines consistently when we 
write prose or poetry

Question 25

Q. What are the rules regarding quotation marks?

Answer 25

Material inside question marks are an exception to the rule.

Question 26

. What happens when you omit a brace or misspell one of the words, like public
or static or void or main?

Answer 26

A. It depends upon precisely what you do. Such errors are called syntax errors and are usually caught by the compiler. For example, if you make a program Bad that is
exactly the same as HelloWorld except that you omit the line containing the first
left brace (and change the program name from HelloWorld to Bad), you get the
following helpful message:
% javac Bad.java
Bad.java:2: ‘{‘ expected
public static void main(String[] args)
^
1 error
From this message, you might correctly surmise that you need to insert a left brace.
But the compiler may not be able to tell you exactly what mistake you made, so the
error message may be hard to understand. For example, if you omit the second left
brace instead of the first one, you get the following messages: % javac Bad.java
Bad.java:4: ‘;’ expected
System.out.print(“Hello, World”);
^
Bad.java:7: ‘class’ or ‘interface’ expected
}

Bad.java:8: ‘class’ or ‘interface’ expected

3 errors
One way to get used to such messages is to intentionally introduce mistakes into a
simple program and then see what happens. Whatever the error message says, you
should treat the compiler as a friend, for it is just trying to tell you that something
is wrong with your program.

% javac Bad.java
Bad.java:4: ‘;’ expected
System.out.print(“Hello, World”);
^
Bad.java:7: ‘class’ or ‘interface’ expected
}

Bad.java:8: ‘class’ or ‘interface’ expected

3 errors
One way to get used to such messages is to intentionally introduce mistakes into a
simple program and then see what happens. Whatever the error message says, you
should treat the compiler as a friend, for it is just trying to tell you that something
is wrong with your program.

Question 27

Can a Java program use more than one command line argument?

Answer 27

You can use as many as you like; but we usually use just a few.

Question 28

What is a command line argument?

Answer 28

What is it, indeed?

Question 29

How many classes are available from the JDK?

Answer 29

One estimate was in the three thousand range!