Natero Code Questions

BlockingQueue.java

import java.util.ArrayList;

class BlockingQueue {
	private ArrayList<Character> queue;

	public BlockingQueue() {
		queue = new ArrayList<Character>();
	}

	public synchronized String take() {
		if (queue.size() == 0) {
			return "Empty queue";
		}
		String toReturn = queue.get(queue.size() - 1).toString();
		queue.remove(queue.size() - 1);
		return toReturn;
	}

	public synchronized void put(String string) {
		char[] tempArr = string.toCharArray();
		if ((queue.size() +  tempArr.length) > 100) {
			return;
		}
		Character[] charObjectArray = new Character[tempArr.length];
		for (int i = 0; i < tempArr.length; i++) {
			charObjectArray[i] = new Character(tempArr[i]);
		}
		for (Character character : charObjectArray) {
			queue.add(character);
		} 
	}

	public static void main(String[] args) {
		BlockingQueue queue = new BlockingQueue();
		queue.put("wimbledon");
		queue.put("fgfsgfgadkfodjfijijijikafhauhuvanrna;k");
		System.out.println(queue.take());

	}
}

Reduce.java

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.BufferedWriter;
import java.io.OutputStreamWriter;
import java.io.FileOutputStream;
import java.util.ArrayList;
import java.util.HashMap;

class Reduce {
	
	public static void reduceByKey(String input1, String input2) {
		ArrayList<String> inputFiles = new ArrayList<String>();
		inputFiles.add(input1);
		inputFiles.add(input2);

		try {
			ArrayList<BufferedReader> fileReads = new ArrayList<BufferedReader>();
			for (String file : inputFiles) {
				fileReads.add(new BufferedReader(new FileReader(new File(file)))); //I'm not sure how to limit this to 100 lines, because there are a varying number of bytes/line.
			}
			HashMap<String, ArrayList> fileHash = new HashMap<String, ArrayList>();
			for (BufferedReader file : fileReads) {
				String line;
				while((line = file.readLine()) != null) {
					String[] keyVal = line.split(",", -1);
					ArrayList<String> temp = fileHash.get(keyVal[0]);
					if (temp == null) {
						temp = new ArrayList<String>();
					}
					temp.add(keyVal[1]);
					fileHash.put(keyVal[0], temp);
				}
			}
			for (BufferedReader file : fileReads) {
				file.close();
			}

			BufferedWriter output = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("output.txt"), "utf-8"));
			for (ArrayList<String> value : fileHash.values()) {
				for (String elem : value) {
					output.write(elem + ",");
				}
				output.newLine();
			}
			output.close();

		} catch (IOException ex) {
			ex.printStackTrace();
		}
	}

	public static void main(String[] args) {
		Reduce.reduceByKey("txt1.txt", "txt2.txt");
	}

}

SortedLists.java

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.BufferedWriter;
import java.io.OutputStreamWriter;
import java.io.FileOutputStream;

class SortedLists {

	public static void mergeFiles(String outputFile, String inputFile1, String inputFile2, String inputFile3) {
		String[] inputFilenames = new String[3];
		inputFilenames[0] = inputFile1;
		inputFilenames[1] = inputFile2;
		inputFilenames[2] = inputFile3;
		String outputFilename = outputFile;	
		
		try {
			BufferedReader[] inputs = new BufferedReader[3];
			int i = 0;
			for (String inputFile : inputFilenames) {
				BufferedReader buffread = new BufferedReader(new FileReader(new File(inputFile)));
				inputs[i] = buffread;
				i++;
			}
			BufferedWriter output = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(outputFilename), "utf-8"));
		
			boolean moreIterations = true;
			boolean advanceInput1 = true;
			boolean advanceInput2 = true;
			boolean advanceInput3 = true;

			String currInput1 = "";
			String currInput2 = "";
			String currInput3 = "";
			while (moreIterations) {
				if (advanceInput1) {
					currInput1 = inputs[0].readLine();
				} 
				if (advanceInput2) {
					currInput2 = inputs[1].readLine();
				} 
				if (advanceInput3) {
					currInput3 = inputs[2].readLine();
				}

				if (currInput1 != null && (currInput2 == null || currInput1.compareTo(currInput2) <= 0) && (currInput3 == null || currInput1.compareTo(currInput3) <= 0)) {
					output.write(currInput1);
					output.newLine();
					advanceInput1 = true;
					advanceInput2 = false;
					advanceInput3 = false;

				} else if (currInput2 != null && (currInput1 == null || currInput2.compareTo(currInput1) <= 0) && (currInput3 == null || currInput2.compareTo(currInput3) <= 0)) {
					output.write(currInput2);
					output.newLine();
					advanceInput1 = false;
					advanceInput2 = true;
					advanceInput3 = false;

				} else if (currInput3 != null && (currInput2 == null || currInput3.compareTo(currInput2) <= 0) && (currInput1 == null || currInput3.compareTo(currInput1) <= 0)) {
					output.write(currInput3);
					output.newLine();
					advanceInput1 = false;
					advanceInput2 = false;
					advanceInput3 = true;
				}
				if (currInput1 == null && currInput2 == null && currInput3 == null) {
					moreIterations = false;
				}


			}
			output.close();
			for (BufferedReader buff : inputs) {
				buff.close();
			} 
		} catch (IOException ex) {
			ex.printStackTrace();
		}
	}

	public static void main(String[] args) {
		SortedLists.mergeFiles("output.txt", "txt1.txt", "txt2.txt", "txt3.txt");
	}
}