Problems # 1: Suppose you have a plain text file. Write a simple java program to find out the first non-repeated word in the file.

FirstNonRepeatedWordFinder.java

package com.therapjavafest.puzzle;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Hashtable;
import java.util.Map;

public class FirstNonRepeatedWordFinder {

	@SuppressWarnings("resource")
	public static String readTextFromFile(String fileName)
			throws FileNotFoundException {
		StringBuilder builder = new StringBuilder();
		File file = new File(fileName);
		// check if file is exist or not, if not exist throw a Exceptions
		if (!file.exists()) {
			throw new FileNotFoundException();
		}

		BufferedReader reader;
		try {
			reader = new BufferedReader(new FileReader(file));
			String line = "";
			while ((line = reader.readLine()) != null) {
				builder.append(line);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
		return builder.toString();
	}

	public static String findNonRepeatedWords(String text) {

		Map<String, Integer> map = new Hashtable<>();
		Integer intgr = null;

		final String[] words = text
				.split("[  \"!#$%&'()*+,-.//:;<=>?@^_`{|}~]"); // split this text using delimiters
														

		for (String str : words) {

			intgr = map.get(str);
			// If there is no value for that word in the
			// map then insert a '1'
			if (intgr == null) {
				map.put(str, new Integer(1));
			} else {
				// else if there is already a value for that word, increment the
				// value by 1
				map.put(str, new Integer(intgr.intValue() + 1));
			}
		}
		System.out.println(map);

		for (String str : words) {
			if (map.get(str).intValue() == 1) {
				return str;
			}
		}
		return null;
	}

	public static void main(String[] args) {
		try {
			System.out.println("First Non Repeated Word is: "
					+ findNonRepeatedWords(readTextFromFile("textfile.txt")));
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}
	}
}