在文本文件中查找唯一的单词

Question

I'm writing this program in Java to find the unique words in a text file. I want to know if this code is correct as it shows even spaces as words.

String[] words;
List<String> uniqueWords = new ArrayList<String>();
words = str1.split("[!-~]* ");
for (int i = 0; i < words.length; i++)
{
    if (!(uniqueWords.contains (words[i])))
    {
        uniqueWords.add(words[i]);
    }
}

For example, if my input is "Hello world! How is the world?" my output array/set/list should have hello, world, how, is, the

Answer 1

You can find unique words by using a Set . Set is a Collection which contains no duplicate elements.

String[] words;
Set<String> uniqueWords = new HashSet<String>();
words = str1.split("[\\W]+");
for (int i = 0; i < words.length; i++)
{
    uniqueWords.add(words[i]);
}

Answer 2

Slightly modified version of other answers (I like it short and simple):

String[] words = str1.split("[!-~]* ");
Set<String> uniqueWords = new HashSet<String>();

for (String word : words) {
    uniqueWords.add(word);
}

Note: if you want to split on ! or - or ~ or space, you should use this:

String[] words = str1.split("[-!~\\s]+");

(the dash must be first or last)

Answer 3

如果我们真的想要紧凑：

Set<String> unique = new HashSet<String>(Arrays.asList(str.toLowerCase().split("[-.,:;?!~\\s]+")));

Answer 4

Set does not allow duplicates where as List allows duplicates.

String[] words;
Set<String> uniqueWords = new HashSet<String>();
words = str1.split("[!-~]* ");
for (int i = 0; i < words.length; i++)
    uniqueWords.add(words[i]); //Here you need not to check with set because it wont allow duplicates

Answer 5

I'd suggest you use pattern and matchers and drop the result in a Set.

public void getWords()
{
    Set<String> words = new HashSet<String>();
    String pattern = "[a-zA-Z]+\\s";
    String match = "hello world how* are. you! world hello";
    Pattern compile = Pattern.compile(pattern);
    Matcher matcher = compile.matcher(match);
    while(matcher.find())
    {
        String group = matcher.group();
        boolean add = words.add(group);
        if(add)
        {
            System.out.println(group);
        }
    }
}

Output:

hello 
world 

Change your definition of what a 'word' is by changing the pattern.

Answer 6

In case if you would like to get the words that have not been duplicated in the sentence/any sort of text, You can try this:

   public static Map<String,Integer> getUniqueWords(String sentence){
   String[] word = sentence.split("[\\W]+");
        Map<String,Integer> uniqueWord = new HashMap<>();
        for (String e:word){
            if(!uniqueWord.containsKey(e)){
                uniqueWord.put(e,1);
            }else{
                uniqueWord.remove(e);
            }
        }
        return uniqueWord;
    }