Hello, World

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UNDER CONSTRUCTION

This assignment is optional. Its sole purpose is to ensure that you can write simple Java programs, use algs4.jar, and submit them to the Coursera autograder.

0. Install our Java programming environment (optional).  Install our novice-friendly Java programming environment on your computer by following these step-by-step instructions for Mac OS X, Windows, or Linux. On each assignment, use the Project from the menu at top.

   As part of these instructions, you will write, compile, and execute the program HelloWorld.java.

   ~/Desktop/hello> javac HelloWorld.java
   
   ~/Desktop/hello> java HelloWorld
   Hello, World
   

   
   

1. Command-line arguments. Write a program HelloGoodbye.java that takes two names as command-line arguments and prints hello and goodbye messages as shown below (with the names for the hello message in the same order as the command-line arguments and with the names for the goodbye message in reverse order).

   ~/Desktop/hello> javac HelloGoodbye.java
   
   ~/Desktop/hello> java HelloGoodbye Kevin Bob
   Hello Kevin and Bob.
   Goodbye Bob and Kevin.
   
   ~/Desktop/hello> java HelloGoodbye Alejandra Bahati
   Hello Alejandra and Bahati.
   Goodbye Bahati and Alejandra.
   

   
   

2. Using algs4.jar. Under construction. Write a program RandomWord.java that reads a sequence of words from standard input and prints one of those words uniformly at random. Do not store the words in an array or list. Instead, use Knuth’s method: when reading the ith word, select it with probability \(1 \,/ \, i\) to be the champion, replacing the previous champion. After reading all of the words, print the surviving champion.

   ~/Desktop/hello> javac-algs4 RandomWord.java
   
   ~/Desktop/hello> java-algs4 RandomWord
   heads tails
   tails
   
   ~/Desktop/hello> java-algs4 RandomWord
   heads tails
   heads
   
   ~/Desktop/hello> more animals8.txt
   ant bear cat dog
   emu fox goat horse
   
   ~/Desktop/hello> java-algs4 RandomWord < animals8.txt
   emu
   
   ~/Desktop/hello> java-algs4 RandomWord < animals8.txt
   bear
   

   Use the following library functions from algs4.jar:

   • StdIn.readString(): reads and returns the next string from standard input.

   • StdIn.isEmpty(): returns true if there are no more strings available on standard input, and false otherwise.

   • StdOut.println(): prints a string and terminating newline to standard output. It’s also fine to use System.out.println() instead.

   • StdRandom.bernoulli(p): returns true with probability \(p\) and false with probability \(1 - p\).

   In order to access these library functions, you must do the following two things:

   • Add algs4.jar to the Java classpath. This typically requires a different mechanism from the command line and the IDE.

     • If you used our autoinstaller, the Bash commands javac-algs4 and java-algs4 add algs4.jar to the Java classpath.

     • If you use IntelliJ, the supplied IntelliJ project folder includes algs4.jar and adds it to the Java classpath.

     • If you prefer to use some other shell (such as Powershell or zsh) or IDE (such as Eclipse or Netbeans), that’s fine—just be sure that you can configure it accordingly.

   • Add an import statement like the following at the top of your program:

     import edu.princeton.cs.algs4.StdIn;
     import edu.princeton.cs.algs4.StdOut;
     import edu.princeton.cs.algs4.StdRandom;
     

     If you use IntelliJ and the provided project folder, IntelliJ will automatically add and remove import statements as needed, so you won’t need to type them.

Web submission. Submit a ZIP file containing only HelloWorld.java, HelloGoodbye.java, and RandomWord.java. Your submission may not call library functions except those in java.lang and the ones in algs4.jar enumerated above.