lab-report-2.md

Lab Report 2

Part 1

Here's my code for my StringServer:

import java.io.IOException;
import java.net.URI;
import java.util.*;

class Handler implements URLHandler {
    String str = "";

    public String handleRequest(URI url) {
        if (url.getPath().contains("/add-message")) {
            String[] parameters = url.getQuery().split("=");
            if (parameters[0].equals("s")) {
                str = str + parameters[1] + "\n";
            }
        } else {
          return str + "\nuse /add-message?s= to add to the string";
        }
        return str;
    }
}

class StringServer {
    public static void main(String[] args) throws IOException {
        if(args.length == 0){
            System.out.println("Missing port number! Try any number between 1024 to 49151");
            return;
        }

        int port = Integer.parseInt(args[0]);

        Server.start(port, new Handler());
    }
}

Here's an example use of my simple search engine:

All of the following URL requests go through the handleRequest(URI url) method

Adding "hello"

• This runs through the handleRequest() method and the first if statement since it has "/add-message"
• Then it goes through the next if statement since the first parameter is "s"
• Then the str field is "hello \n"

Adding "world"

• Runs through the same path as previous URL request.
• Now, str field is "hello \n world \n"

Part 2

The following tester method would fail the JUnit test.

We would initially remove the smallest element (1.0), and the average should be (1.0 + 2.0 + 3.0)/3 = 2.0. However, the method returns 3.6666. This is because the method removes all doubles equal to the smallest element, so it removes both 1.0s, leading to the erroneous calculation.

double[] input1 = {1.0, 1.0, 2.0, 3.0};
assertEquals(2.0, ArrayExamples.averageWithoutLowest(input), 0.0);

Whereas this JUnit test would not induce a failure.

This method does not induce a failure because there is only one instance of the smallest element, 1.0. Therefore, it will function correctly and get the correct 2.5 average.

double[] input2 = {1.0, 2.0, 3.0};
assertEquals(2.5, ArrayExamples.averageWithoutLowest(input2), 0.0);

Leads to this error from JUnit:

The original buggy code was:

static double averageWithoutLowest(double[] arr) {
    if(arr.length < 2) { return 0.0; }
    double lowest = arr[0];
    for(double num: arr) {
      if(num < lowest) { lowest = num; }
    }
    double sum = 0;
    for(double num: arr) {
      if(num != lowest) { sum += num; }
    }
    return sum / (arr.length - 1);
  }

I fixed it to be:

static double averageWithoutLowest(double[] arr) {
    if(arr.length < 2) { return 0.0; }
    double lowest = arr[0];
    for(double num: arr) {
      if(num < lowest) { lowest = num; }
    }
    double sum = 0;
    for(double num: arr) {
      sum += num;
    }
    sum -= lowest;
    return sum / (arr.length - 1);
  }

• I deleted the if statement within the for loop and then just subtracted the lowest number.
• The problem with the original code was that when there was that if there were two or more values that coincided with lowest, it would not include both of them.
• My fix includes all the values and subtracts the lowest so it will only remove one value

Part 3

• Week 2 introduced me to the URIHandler interface in Java. I learned how to handle URI/URLs in Java and a simple overview of how they work with queries and other simple features.