Intro to Java
Programming
Prof. Gregory Safko
Camden County College
1.
Know how to write Welcome.java
from memory
2.
Know the difference between a .java
file and a .class file
3.
Know the major differences between Java programs and Java applets
4.
Know the difference between a
compiler program and an interpreted program, and why Java can be considered a
program that contains both behaviors.
5.
Know the 2 ways to write comments
6.
Know the import
command and why it is needed
7.
Know the extends
command and why it is needed
8.
Know how to use command line arguments (String args[ ])
9.
Know how to use the SafkoInput
class
10.
Know the two methods of the JOptionPane
object that we discussed in class
11.
Know the difference between and when to use Integer.parseInt( )
and Double.parseDouble( )
12.
Know when to put a semi-colon ( ;
) at the end of statements
13.
Know the difference between the .println( )
method and the .print( ) method
14.
Know how to typecast integers
to doubles,
and vice verse
15.
Know the difference between =
and ==,
and why the statement if(a = 1) is a compiler error
16.
Know why you would use the keyword final
17.
Know the four parameters used in the JOptionPane.showMessageDialog( )
method
18.
Know the two parameters used in the JOptionPane.showInputDialog( )
method
19.
Know why you need System.exit( 0 );
when ending programs that use JOptionPane
20. What are the 6 comparison
operators?
21. What is the proper way to
use a while
loop? A do-while
loop?
22.
What is the proper way to use the if statement? The if-else
statement?
23. Know the use and difference between the pre- and post- increment and decrement operators (++a, a++, --a, a--)
Multiple Choice
Consider the following
question:
Java is very similar to _____
because they are both _____ languages
a.
BASIC, interpreted
b.
BASIC, compiled
c.
C++, interpreted
d.
C++, compiled
There are two correct
answers to this question (a and d). Can you explain why?
Sample Programs
Write
a program that will take two numbers and will find their average.
Write it using SafkoInput, as follows:
Write it using JOptionPane, as follows:
What
would be the problem if you entered a 3 and 4, and instead of displaying 3.5, it
displays 3?
Debugging
Correct
what is wrong with the following (there may be more than one thing wrong).
Assume the all the appropriate imports and variables have been declared.
1.
// This will test if a number equals 0
int
x;
x
= SafkoInput.readInt();
if
(x = 0)
System.out.println(“It’s zero");
2.
// This will test if a number is negative
int
a;
a
= SafkoInput.readInt();
if
a < 0
System.out.println(“It’s negative");
else
System.out.println(“It’s
positive");
3.
// This will test if a number is negative
int a;
a
= SafkoInput.readInt();
if (a
< 0);
System.out.println(“It’s negative");
else
System.out.println(“It’s
positive");
else
System.out.println(“I
can’t tell");
4.
// This code will loop while k not equal to zero
int
b,k;
b
= SafkoInput.readInt();
k
= b/2;
while
k != 0
{
if
k = b
System.out.println(“It’s
even");
else
System.out.println(“It’s
odd");
}
5.
// This code will test if m is even
int
m,p;
p =
m/2;
System.out.print(“Enter
a number: ");
m
= SafkoInput.readInt();
if (m
= 2 * p)
System.out.println(m
+ “ is even");
else
System.out.println(m
+ “ is odd");
6.
// This code will run until the user enters a number less than 10
System.out.print(“Enter
a number greater than 10: ");
j
= SafkoInput.readInt();
while
(j <= 10)
{
if
(j % 2 == 0)
cout << j << "is even";
System.out.print(“Enter
a number greater than 10: ");
}
7.
// This code will test if a number is unequal to 5
System.out.print(“Enter
a number: ");
final
int f = 5;
w
= SafkoInput.readInt();
if
(w <=> 5)
System.out.println(“This
number is not 5");
8.
// This code will display a number, and it’s "half"
double
m,n;
n
= m/2;
System.out.print(“Please
enter a number: ");
m
= SafkoInput.readInt();
System.out.println(“m
is: "+"m");
System.out.println(“m
cut in half is: "+ n);
9.
// This is just a control structure. Why won’t it compile?
int x
= 1;
while
(x <= 10);
x++;
}
Short
answers:
Why
could the loop in question #4 be an infinite loop?
Under
what conditions would you use a do/while
loop rather than a while
loop?