Transcript java_slidesx

Game Programming in Java
Dr. Jeyakesavan Veerasamy
CS faculty, The University of Texas at Dallas
Email: [email protected]
Website: www.utdallas.edu/~jeyv
Goals
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Understand C++ vs. Java concepts
Strengthen recursive coding skills
See algorithm efficiency in action
Strengthen logical thinking skills
Strengthen coding skills in Java
Event driven programming
This is NOT a “serious” game programming
workshop!
C++ vs. Java: Similarities
• Both support OOP. Most OOP library contents
are similar, however Java continues to grow
faster.
• Syntax is very close – Java has strong influence
of C/C++. Easy to learn the other language
when you know one of these.
C++ Compiler & Linker expectations
file1.cpp
file2.cpp
Compiler
Compiler
file1.o
file2.o
….
filen.cpp
Compiler
….
filen.o
Linker
application
(executable)
C++ compiler does not
care about filenames.
Java?
file1.java
file2.java
file3.java
…
filen.java
C++ Concepts: Operator overloading
• Operator overloading:
ComplexNumber x, y, z;
z = x + y;
• In Java?
C++ Concepts: Method overloading
• Method overloading – similar to Java
– use different argument types to differentiate
C++ Concept: Friend
• friend designation - breaks OOP philosophy!
– specific functions/methods outside the class can
access private data  Why?
Concepts: Objects
• Objects can be created as local variables just
like any basic data types.
ComplexNumber num1;
Arrays
• Basic data types and classes are treated the
same way in C++, unlike Java.
ComplexNumber numbers[5];
C++ Array version #2
ComplexNumber *numbers;
numbers = new ComplexNumber[5];
C++ Array version #3
ComplexNumber **numbers;
numbers = new ComplexNumber*[5];
for( index i = 0 ; i < 5 ; i++)
numbers[i] = new ComplexNumber(…);
Java
ComplexNumber numbers[];
numbers = new ComplexNumber[5];
for( index i = 0 ; i < 5 ; i++)
numbers[i] = new ComplexNumber(…);
C++ Pointers vs Java References
• Explicit in C++: ComplexType *cnump;
• Pointer arithmetic
• Dynamic memory allocation requires pointers
(just like references in Java)
Dynamic memory allocation
• No automatic garbage collection in C++
• # of new invocations should match # of delete
invocations.
• If a class constructor allocates memory (i.e.
uses “new …”), it needs a destructor method
too – it should use “delete …” to release
allocated memory.
C++ vs. Java: differences
C++
Java
Write once, compile everywhere  unique
executable for each target
Write once, run anywhere  same class
files will run above all target-specific JREs.
No strict relationship between class names
and filenames. Typically, a header file and
implementation file are used for each class.
Strict relationship is enforced, e.g. source
code for class PayRoll has to be in
PayRoll.java
I/O statements use cin and cout, e.g.
cin >> x;
cout << y;
I/O input mechanism is bit more complex,
since default mechanism reads one byte at
a time (System.in). Output is easy, e.g.
System.out.println(x);
Pointers, References, and pass by value are
supported. No array bound checking.
Primitive data types always passed by value.
Objects are passed by reference. Array
bounds are always checked.
Explicit memory management. Supports
destructors.
Automatic Garbage Collection.
Supports operator overloading.
Specifically operator overloading was left
out.
Example: Guessing game
• Think of a number between 1 and 100 in your
mind. Then, the computer (program) will ask
you a series of questions and determine that
number based on your answers.
Series of interactions:
Program: Is it NN?
Your response: <, =, or >
Sample run #1
Guess a number between 1 and 100 (both inclusive)
and get ready to answer a few questions.
How about 50 (<,=,>)? <
How about 25 (<,=,>)? <
How about 12 (<,=,>)? >
How about 18 (<,=,>)? >
How about 21 (<,=,>)? <
How about 19 (<,=,>)? >
Your guess is 20.
Sample run #2
Guess a number between 1 and 100 (both inclusive)
and get ready to answer a few questions.
How about 50 (<,=,>)? >
How about 75 (<,=,>)? <
How about 62 (<,=,>)? >
How about 68 (<,=,>)? >
How about 71 (<,=,>)? =
Your guess is 71.
Example: Lotto game
• Generate 6 unique numbers from 1 to 50.
• Output should NOT have repeating numbers.
Random ran = new Random();
int x = ran.nextInt(50); //returns 0 to 49
Example: Hangman game
Programming Competitions:
usaco.org
Create a new account in usaco.org
Use graduation year 9999, country code IND
Then go to your email to find the password.
Login first, then go to
www.usaco.org/index.php?page=nov12problems
look into Bronze level problems
USA Computing Olympiad training site
ace.delos.com/usacogate
You need to create an account (use KITE email
address) to gain access.
100s or 1000s of programming problems!
A few solution files are @
www.utdallas.edu/~jeyv/compete
Example: Knapsack problem
int weights[] = { 5, 9, 23, 12, 45, 10, 4, 19, 53 };
int target = 100;
Goal is to find 2 distinct weights, when added,
come to close to target, but do NOT exceed it.
For this problem, answer is 45 and 53.
Now, let us write generic algorithm so that we
can find it for any user-specified target value.
Memory game
• GUI setup code
• Image files