Dick Steflik

CS-240 Dick Steflik

What is going on ? • CS-140 – Intro to Programming – Java

• CS-240 – Data Structures (definitely not intro) – C++

Java or C++

C++ this semester • Data Structures are language independent • C++, it’s just another language • The syntax of Java and C++ are very similar – the symantics are different, we’ll investigate those differences

• Both support object orientation

Java • Interpreted • optimized for the internet • Derived from C++ • Good object model • Widely accepted as the internet programming language • about 10 years

C++ • Compiled • optimized for workstation usage • derived from C • Poorer object model • Widely accepted as workstation programming language • about 15 years old

This semester… • You’ll learn quit a lot of C++ • More about OOP • Get an intuitive introduction to Algorithms and Algorithm Analysis

The Java Compiler • Translates Java source code into java bytecodes – java bytecodes are the machine language for the Java Virtual Machine • the JVM is a hypothetical machine that written mostly in Java but a little bit in C++ and is compiled specifically for various platforms (Windows, Sun, HP, LINUX)

• Bytecodes are portable between platforms

The C++ Compiler • Translates C++ source code into the machine language for the hardware platform – output of the compiler are object files (.obj) which are partially ready to run – object files must be linked together using the system linker to make an executable file (.exe) • .exe files are specific for the hardware platform

• C++ is portable only at the source level

Java import statements • imports indicate which parts of which java packages an application will need at run time – also allows the compiler to run to completion and not indicate that the class isn’t part of the file being compiles

• Remember the compiler only works with the file being compiled

C++ include statements • indicate to the compiler preprocessor which files (source) to include in the file to be compiled. Included files are actually copied into the source file and replace the #include statement.

Java application • is defined as a class that is instantiated when the program is run • main() is the name of the function to be run initially • constructor is used initialize the class

C++ application • classes are/can be used by a C++ application; but the application is not itself an instantiated class (like Java) • main() is the name of the function where the executable file starts execution • C++ classes do not have main() functions • C++ objects are initialized via class constructors, C++ applications are initialized in the main() function.

Java - HelloWorld public class HelloWorld { public static void main(String args[]) { System.out.println(“Hellow World”); } }

C++ - HelloWorld #include

int main() { cout << “Hello World” << “\n”; }

Java Application Development classpath

Java Source File

javac

Java Class File

JVM

Compile into bytecodes base classes

Run the program

C++ application development

C++ Source File C++ Include Files

compiler

Object File

System Object Files

Linker

.EXE File