Java Basic Syntax

Java to C++ comparizon
First program
Basic Java syntax
Version control system
Java Basic Syntax
Java vs C++
Wojciech Frohmberg1
1 Department
of Computer Science
Poznan University of Technology
2012.10.07 / OOP Laboratory
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
Outline
1
Java to C++ comparizon
2
First program
3
Basic Java syntax
4
Version control system
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
Outline
1
Java to C++ comparizon
2
First program
3
Basic Java syntax
4
Version control system
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
Outline
1
Java to C++ comparizon
2
First program
3
Basic Java syntax
4
Version control system
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
Outline
1
Java to C++ comparizon
2
First program
3
Basic Java syntax
4
Version control system
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
Tabular comparizon
Paradigm
Compilation/Running
Standard libraries
Multiple inheritance
Run-time object information
Type instances passing
C++
Procedural/Object-oriented
Compiled to machine code that can run on
specific system
Limited to the very basic functionality (e.g.
STL supports regular expression only since
C++11)
Full support, including virtual inheritance
Java
Object-oriented is highly recommended
Compiled to byte code that can be run on
system with JVM
Grows with each release
One can achieve similar result using interfaces
Only type names are available
Full meta-information support, including dynamic code invocation
by value/by reference/by pointer
instances of primitive types by value, rest
by reference (that can be perceived as
pointers)
explicit – one has to force system to free disposing memory is managed by, so
memory
called, garbage collector
most of operators can be overloaded
does not allow to overload operators
Memory
management
Overloading operators
Logic program hierar- namespaces
chy
Inline abstract class- not possible
es/interfaces implementation
Wojciech Frohmberg
package = path to the source file, filename
= inner type name
allowed
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
Hello world in Java
Java source code
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C++ source code
package hw;
import java.lang.System;
public class Hello {
public static void main(String args[]) {
System.out.println("Hello world");
}
}
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#include <iostream>
using std::cout;
using std::endl;
int main(int argc, char **argv) {
cout << "Hello world" << endl;
}
Compiling
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javac path/to/file/FileName.java
Running
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java path.to.file.FileName
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
Creating jar file
Compiled classes by javac are stored as files with extension
class in a file system. While application grows there are plenty of
such class files. To make the application transferable one have
to use some other mechanisms that merge the number of files in
a single executable application. To handle this problem Java
applications make use of jar files.
Command creating jar
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jar cfe path/to/jarfile/jarfilename.jar path.to.mainclass.MainClass classfile[, ...]
Running jar
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java -jar jarfile.jar
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
Tasks
Complete the tasks, answer questions
1
Create hello world application in Java and create executable
executable jar file.
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
A few guidelines
Access modifier (without colon) before every class member
declaration
Inheritance of classes using extends keyword
Implementing interface using implements keyword
To declare constant values use final keyword
To use some class from outside of the package use import
keyword
Virtual methods don’t have to be additionally specified – every
method is virtual and can be overridden
To declare abstract method use abstract keyword
Use dot to access members of the object instance
Use dot to access the package elements
Use dot to access a static class members
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
Example
car/Car.java
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package cars;
import vehicles.Vehicle;
import vehicles.IStartEnginable;
public class Car extends Vehicle implements IStartEnginable {
public int cylinders = 10;
public void startEngine() {
System.out.print("B");
for (int i = 0; i < this.cylinders; i++) {
System.out.print("R");
}
System.out.println();
}
public static void main(String[] args) {
Car car = new Car();
car.startEngine();
}
}
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
Tasks
Complete the tasks, answer questions
1
Use a class hierarchy from the first presentation (car.h/cpp,
volkswagen.h/cpp, hyundai.h/cpp, main2.cpp) and rewrite its
functionality to Java language. Remember to create a jar
file.
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
What for?
Version control system allows to manage the changes in the
project. It can serve to monitor the project progress, restore
code after getting into dead-end path, tracking the differences
between files or even automated merging of changes of a single
file by two programmers.
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
Git
To our todays laboratories purpose we will use git tool as it is
available on polluks server. It though isn’t the most user-friendly
one, but it will serve only to show how to make use of the
powerful tool of version control system.
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
Basic use case
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
How to use(1)
On server side (initialization)
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ssh [email protected]
#enters to polluks
mkdir gittut
cd gittut/
git init
echo "Sample text" > sample.txt
git status
git checkout dumpbranch
#creates repositorium directory
#enters the repo directory
#initializes repo
#creates first repo file
#prints the changes in repo says that
#that sample.txt hasn’t been yet tracked
#adds the sample.txt to tracked files
#commits changes
#shows available branches
#creates dumpbranch to use master branch
#without collision
#switches to dumpbranch
exit
#exits the server
git
git
git
git
add sample.txt
commit -m "First commit"
branch
branch dumpbranch
Wojciech Frohmberg
Java Basic Syntax
Java to C++ comparizon
First program
Basic Java syntax
Version control system
How to use(2)
On client side (cloning repo and first push)
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#downloads the repo to client
git clone ssh://[email protected]/home/infXXXXXX/gittut
cd gittut
echo "Sample text2" >> sample.txt
git status
git commit -a -m "sample.txt modified"
git diff sample.txt
git push origin master
git log
git pull origin master
#enters the repo directory
#adds line to sample.txt
#shows changes in repo
#commits changes in sample.txt
#shows changes on sample.txt
#since previous commit
#inserts changes into server
#into master branch
#shows the log of the repo
#gets commits currently
#available on remote server
Wojciech Frohmberg
Java Basic Syntax