Methods and tools for big data Lab 1

VE472 — Methods and tools
for big data
Lab 1
Goals of the lab
• Write and use packages in Java
• File input and output in Java
• Object-oriented programming in Java
1 Introduction
In this lab we assume a good C++ background and help you turning it into the ability of Java
programming. A simple guideline can be found in the appendix A.
Your friend Reapor Rich plans to build a new type of cinema in Singapore. The seats are assigned
automatically by a seat management system when customers buy tickets. The structure of a typical
cinema hall is shown on figure 1, and we can observe that three seats are selected.
Figure 1: Structure of a typical cinema hall.
When people choose their seat they always want to stay together and prefer the seats in the middle and
back of the cinema. In figure 1, your other friends, Krystor, Frank, and Simon selected the three best
seats in the hall.
According to this golden rule, the management system will assign the seats within the following rules:
• When a customer wants to buy n tickets, the system always selects n consecutive seats on a row.
The seats are “consecutive” means that they are next to each on the same row.
• The system always selects the seats closest to the middle back of the cinema hall. It means that
the distance between the centroid of the seats and the middle back point (row 8, column between
6 and 7 on figure 1) should be minimized.
• When two selections on different rows have the same distance, choose the row with the larger row
number.
• When two different selections on one row have the same distance, choose the centroid on the left.
• If no selection satisfies the rules above, deny the customer’s request of buying tickets.
For example on figure 1, as the centroid is (8, 6), and the middle back point (8, 6.5),then the distance is
0.5, which is the smallest in all selections.
Hint: you are not recommended to use square root when comparing the distance, as it may lose some
accuracy. This also applies to the analysis of big data composed of integers.
2 Java environment setup
In this section we install the Java environment and learn how to create and install basic Java packages.
2.1 Installation
First you need a Java SDK (Java Software Development Kit, or JDK) installed on your system. There
are two implementations for Java platform programming: Oracle JDK (preferred), the official Oracle
version of Java Development Kit; and OpenJDK a free and open-source implementation of the Java SE
Platform Edition. For this course, you should install Java 8 or above.
2.1.1 Windows
Windows is not recommended in this course. If you really want to use Java on Windows, download
Oracle JDK from https://www.oracle.com/technetwork/java/javase/downloads/index.html and run the
installer.
2.1.2 Linux
• Debian and derived distribution, e.g. Ubuntu, Linux Mint.
sh $ apt-get update
sh $ apt-get install software-properties-common
sh $ add-apt-repository <repository>
sh $ apt-get update
sh $ apt-get install oracle-java<X>-installer
Replace <repository> with a third-party repository, and <X> with the version number. Third-party
repositories can be found at https://launchpad.net/, e.g. Java 8: ppa:webupd8team/java, or Java
12: ppa:linuxuprising/java1
.
• Arch Linux and derived distributions, e.g. Manjaro: first install yay.
sh $ sudo pacman -S git
sh $ git clone https://aur.archlinux.org/yay.git
sh $ cd yay
sh $ makepkg -si
1Reference: https://www.linuxuprising.com/2019/03/how-to-install-oracle-java-12-jdk-12-in.html.
Display all available Oracle JDK and JRE versions and select whichever you want.
sh $ sudo pacman -Syyu
sh $ yay jdk
• Other: use a proper search engine and share your findings such that we can update this guide.
2.1.3 Mac OS
Download Oracle JDK from https://www.oracle.com/technetwork/java/javase/downloads/index.html
and run the installer.
2.2 Java package creation
In this part, you need to create a simple Java command line program. Different from C++, Java programs
are managed in packages, for example, for this lab, a typical package structure is as follows.
Current directory
com
ve472
l1
Main.java
Content of Main.java2
.
1 package com.ve472.l1;
2
3 public class Main {
4
5 public static void main(String[] args) {
6 // write your code here
7 }
8 }
2.3 Third-party package installation
The built-in support for third-party packages is one of the most fascinating features of Java compared
to C++. The org.apache.commons.cli package is used in this lab to parse command line arguments. It
is also the cli parser of Hadoop, which will be used in future labs.
There are two ways to install packages: direct install or through a package manager, such as maven. We
recommend you to latter option.
2.3.1 Direct package installation
If you use common IDEs, e.g. Eclipse or Intellij Idea, you can manually add third-party libraries. First,
download the binary file of the third-party libraries. Apache Commons CLI can be downloaded from http:
2Reference: https://docs.oracle.com/javase/tutorial/java/package/namingpkgs.html.
//commons.apache.org/proper/commons-cli/download_cli.cgi. Then add *.jar to your modules in the
modules settings.
To include third-party libraries using the command line.
sh $ javac -classpath <path_to_libraries> <path_to_program>
Replace <path_to_libraries> with your own path to the third party libraries and <path_to_program>
with your program. For more information refer to https://docs.oracle.com/javase/8/docs/technotes/
tools/windows/classpath.html.
2.3.2 Maven package installation
Most IDEs, e.g Eclipse or Intellij Idea, officially support maven. Upon creating a maven project, a pom.xml
file is generated. You can add dependencies and define the JDK version to use.
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>ve472</groupId>
<artifactId>ve472l1</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<!-- https://mvnrepository.com/artifact/commons-cli/commons-cli -->
<dependency>
<groupId>commons-cli</groupId>
<artifactId>commons-cli</artifactId>
<version>1.4</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
<configuration>
<source>8</source>
<target>8</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
For more information on how to use maven from the command line refer to https://maven.apache.org/
guides/getting-started/maven-in-five-minutes.html.
3 Java programming
Now that is environment is ready we start solving our initial problem using a Java program.
3.1 Command Line Arguments
Import the org.apache.commons.cli package3
.
1 import org.apache.commons.cli.*;
This package provides several useful classes such as Options, CommandLineParser, and HelpFormatter.
Task
Use them to write a command line program which takes two normal arguments (--hall and --query),
as well as a help argument (-h/--help).
When one of the two arguments is missing, or -h/--help is used, output a help information generated
by HelpFormatter. The format is
1 usage: cinema
2 -h,--help print this message
3 --hall <arg> path of the hall config directory
4 --query <arg> query of customer orders
3.2 Configuration files
The information about the halls in the cinema is stored in a configuration directory specified using the
--hall flag (section 3.1). This directory contains several files but the their names are not fixed.
Write a class Hall which reads a cinema hall configuration files and saves all of the information as
attributes. It is recommended to use a two-dimension List<Boolean> to store the seats.
Format of a cinema hall configuration file.
• Hall name: unique, on the first line;
• Movie name: not unique, on the second line;
• m boolean values on each of the following n lines: a location with a seat shows a 1 and a 0
otherwise; m is the maximum length over all the rows;
• Center line: between column m/2 and m/2 + 1, if m is even and on column (m + 1)/2, otherwise;
The column number starts at 1;
3Reference: https://commons.apache.org/proper/commons-cli/.
Task
Write a class Cinema which parses the configuration files in the directory, using the --Hall flag, and saves
the information as attributes. It is recommended to use a HashMap<String, Hall> to store the mapping
between hall names and Halls, and a HashMap<String, List<Hall>> to store the mapping between movie
names and Halls.
Example
A valid configuration file looks as follows.Note that spaces are allowed in the hall and movie names.
apple
The Wandering Earth
1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1
3.3 Answer queries
The tickets purchase requests are stored in a query file defined using the command line argument
--query (section 3.1). The format of each line composing the query file is
customer name,movie name,ticket number n
We assure n > 0, and no comma “,” in the customer and movie names. However spaces are allowed.
Omit all trailing spaces around a comma.
Task
Read the file line by line and answer each query to stdout using the following format:
customer name,movie name,hall name,row number,column number 1,...,column number n
First assign customers to halls, sorted in alphabetical order; start with the first hall. If no seats can be
assigned, or the movie cannot be found, then only print the customer’s name and movie.
Warning: do not print any unnecessary spaces, or some tests might fail on JOJ.
Example
For the input file,
Krystor He , The Wandering Earth, 3
Manuel,The Wandering Earth,20
Jing,unknown,1
The output should be
Krystor He,The Wandering Earth,apple,8,5,6,7
Manuel,The Wandering Earth
Jing,unknown
4 JOJ submissions
Compress your source code into a tar or zip archive following the structure below. Then submit it on
JOJ (https://joj.sjtu.edu.cn).
com
ve472
l1
Cinema.java
Hall.java
Main.java
Note: only the correctness of the implementation will be checked, i.e. its efficiency will not be evaluated.
A The C++ Hitchhiker’s Guide to the Javanian Galaxy
Java is a compiled language, yet it runs on the Java Virtual Machine (JVM).
Java programs need to be compiled and run on a runtime called Java Runtime Environment (JRE). The
Java development environment requires a package called Java Development Kit (JDK).
Java is fully object-oriented.
Java programs are organized in terms of classes. All variables or functions must reside within the scope
of a class. All classes always inherit a common base class “Object”.
The Java memory management features a garbage collector.
Object are automatically deleted and recycled when no longer needed. However, in some cases, you have
to pay a significant performance price for that feature. Stay alert.
Java is statically and weakly typed.
Like C++, all Java variables are typed, and their type must be known at compile time. If necessary
variables can be cast.
Java objects are always passed by reference.
Java contains a few built-in types that are passed by value. However all objects are passed by valuereferences. Think of them as pointers that automatically dereferences themselves.
Java is polymorphic by default.
By default, all methods in a class are “virtual”. Subclasses always override base class objects.
Java allows only single Inheritance and features Interfaces.
Only single inheritances are allowed. Interfaces in Java are similar to pure abstract base classes in C++.
Generics are done by type-erasure.
Java also supports Generic containers, similar to std::vector<> or std::list<> in C++. However, unlike
C++, Java uses type-erasure to handle generics. In contrast, C++ uses type specialization.
Java supports reflection and introspection.
It is possible to ask a class to print out its supported methods, or look up a class by string, at runtime.
Have fun with Java.
Yep. Enjoy Coding!