使用数组查找Java中2个文本文件中包含的唯一单词的列表

Question

I need to read two text files and display all the unique words in both the text files.(the words in both 2 files can only be printed once)

file1.txt

lion

tiger

cheetah

elephant

cow

file2.txt

mouse

dog

cow

cat

lion

expected output :

lion tiger cheetah elephant cow dog cat mouse

public class Workshop {

static int count1 = 0;
static int count2 = 0;

private static final String FILE1 = "C:\\Users\\shagi\\Desktop\\file1.txt";
private static final String FILE2 = "C:\\Users\\shagi\\Desktop\\file2.txt";

static String arrayLines1[] = new String[countLines(FILE1)];
static String arrayLines2[] = new String[countLines(FILE2)];
static String totalArray[] = new String[arrayLines1.length + arrayLines2.length];
static String arrayLines1new[]=new String[countLines(FILE1)];
static int flag = 0;
static int k=arrayLines1.length;

public static void main(String[] args) throws IOException {
    readFile(FILE1, FILE2);
    displaySimilar();
    displayAll();
}

public static int countLines(String File) {
    int lineCount = 0;
    try {
        BufferedReader br = new BufferedReader(new FileReader(File));
        while ((br.readLine()) != null) {
            lineCount++;
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return lineCount;
}

public static void readFile(String File1, String File2) {
    String contents1 = null;
    String contents2 = null;
    try {
        FileReader file1 = new FileReader(File1);
        FileReader file2 = new FileReader(File2);
        BufferedReader buf1 = new BufferedReader(file1);
        BufferedReader buf2 = new BufferedReader(file2);
        while ((contents1 = buf1.readLine()) != null) {
            arrayLines1[count1] = contents1;
            count1++;
        }
        while ((contents2 = buf2.readLine()) != null) {
            arrayLines2[count2] = contents2;
            count2++;
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

There are two methods which i tried to find the ans for my question Method 1

public static void displayAll() {
    for (int i =0; i<k-1;i++){
        System.out.println(totalArray[i]);
    }

    System.out.println(totalArray[k-1]);
    System.out.println("");
    int p=0;
    for (int i=0;i<arrayLines2.length;i++){
        for (int j=0;j<arrayLines1.length;j++){
            if (arrayLines2[i].equals(arrayLines1[j])){
                flag=1;
                break;
            } else {
                flag=0;
            }
            if (flag==1){
                arrayLines1new[p]=arrayLines2[i];
                p++;
            }
        }
    }

Method 2

 public static void displayAll() {
    for (int i=0;i<arrayLines1.length;i++){
        String a=arrayLines1[i];
        for (int j=0;j<arrayLines2.length;j++){
            String b =arrayLines2[j];
            if (!a.equals(b)){
                System.out.println(a);
            }
        }
    }
 }

But both doesnt give the expected output

Answer 1

This would be a good situation for a HashMap. The keys would be the words and the values would be the number of occurrences. You could then print out the keys with a value of 1. The pseudo code would look like this:

1. Initialize the map: HashMap <String, Integer> wordMap = new HashMap<>();
2. For each file:
3. -- For each word:
4. ---- Put the word in wordMap with the appropriate value.
5. For each key in wordMap :
6. -- If wordMap.get(key) == 1 , print out the key

You could also accomplish the same thing using two arrayLists, using one to keep track out the words and another to keep track of the counts.

Both methods have an O(N) time complexity, but using the map is more performant because the maps's values can be updated in O(1).

Answer 2

There is lot of redundant code. Here is a simpler and shorter version.

I am using Set and its operations to find common (intersection), uncommon and all unique words.

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.HashSet;
import java.util.Set;

public class Workshop {

    private static final String FILE1 = "C:\\Users\\shagi\\Desktop\\file1.txt";
    private static final String FILE2 = "C:\\Users\\shagi\\Desktop\\file2.txt";

    static Set<String> file1Words = new HashSet<String>();
    static Set<String> file2Words = new HashSet<String>();
    static Set<String> allWords = new HashSet<String>();
    static Set<String> commonWords = new HashSet<String>();
   static Set<String> uncommonWords = new HashSet<String>();

    public static void main(String[] args) throws IOException {
        file1Words.addAll(readFile(FILE1));
        file2Words.addAll(readFile(FILE2));
        System.out.println("file1  : " + file1Words);
        System.out.println("file2  : " + file2Words);
        displaySimilar();
        System.out.println("common : " + commonWords);
        displayAll();
        System.out.println("all    : " + allWords);
         displayUnCommon();
        System.out.println("uncommon : " + uncommonWords);
    }

    public static void displaySimilar() {
        commonWords.addAll(file1Words);
        commonWords.retainAll(file2Words);
    }

    public static void displayUnCommon() {
         uncommonWords.addAll(file1Words);
        uncommonWords.addAll(file2Words);
        uncommonWords.removeAll(commonWords);
    }

   public static Set<String> readFile(String file) {
        Set<String> words = new HashSet<String>();
        try {
            FileReader fileReader = new FileReader(file);
            BufferedReader buffer = new BufferedReader(fileReader);
            String content = null;
            while ((content = buffer.readLine()) != null) {
                words.add(content);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return words;
    }

    public static void displayAll() {
        allWords.addAll(file1Words);
        allWords.addAll(file2Words);
    }
}

Sample Run:

file1  : [lion, cheetah, tiger, elephant, cow]
file2  : [lion, mouse, cat, cow, dog]
common : [lion, cow]
all    : [cheetah, lion, cat, mouse, tiger, elephant, cow, dog]
uncommon : [cheetah, cat, mouse, tiger, elephant, dog]