How to write a replaceAll function java?

Question

I'm trying to write a program that will allow a user to input a phrase (for example: "I like cats") and print each word on a separate line. I have already written the part to allow a new line at every space but I don't want to have blank lines between the words because of excess spaces. I can't use any regular expressions such as String.split(), replaceAll() or trim().

I tried using a few different methods but I don't know how to delete spaces if you don't know the exact number there could be. I tried a bunch of different methods but nothing seems to work.

Is there a way I could implement it into the code I've already written?

  for (i=0; i<length-1;) {
      j = text.indexOf(" ", i); 
      if (j==-1) {
          j = text.length(); 
      }
      System.out.print("\n"+text.substring(i,j));
      i = j+1; 
  }

Or how can I write a new expression for it? Any suggestions would really be appreciated.

text.replaceAll(" ", "\n") OR if you want a list of lines, text.split("\n") — Vilsol
– Vilsol, Commented Mar 18, 2016 at 4:17
How is this replaceAll? If you want to print each word on a newline, sounds more like you want to implement split — OneCricketeer
– OneCricketeer, Commented Mar 18, 2016 at 4:21
Did you find any of the solutions below useful? if so, please consider leaving feedback by selecting one as the correct answer — frankelot
– frankelot, Commented Mar 18, 2016 at 6:14

Akash Thakare · Accepted Answer · 2016-03-18 04:35:26Z

2

I have already written the part to allow a new line at every space but I don't want to have blank lines between the words because of excess spaces.

If you can't use trim() or replaceAll(), you can use java.util.Scanner to read each word as a token. By default Scanner uses white space pattern as a delimiter for finding tokens. Similarly, you can also use StringTokenizer to print each word on new line.

String str = "I like    cats";
Scanner scanner = new Scanner(str);
while (scanner.hasNext()) {
    System.out.println(scanner.next());
}

OUTPUT

I
like
cats

edited Mar 18, 2016 at 4:35

answered Mar 18, 2016 at 4:22

Akash Thakare

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2 Comments

Vilsol Over a year ago

He is not allowed to use trim() or replaceAll()

frankelot Over a year ago

Upvoted, this is actually pretty elegant. However, Scanner uses regular expressions internally, not sure if OP is fine with that.. if so, this answer is spot on

Vilsol · Accepted Answer · 2016-03-18 04:24:59Z

Here is a simple solution using substring() and indexOf()

public static void main(String[] args) {
    List<String> split = split("I like cats");
    split.forEach(System.out::println);
}

public static List<String> split(String s){
    List<String> list = new ArrayList<>();
    while(s.contains(" ")){
        int pos = s.indexOf(' ');
        list.add(s.substring(0, pos));
        s = s.substring(pos + 1);
    }
    list.add(s);
    return list;
}

Edit:

If you only want to print the text without splitting or making lists, you can use this:

public static void main(String[] args) {
    newLine("I like cats");
}

public static void newLine(String s){
    while(s.contains(" ")){
        int pos = s.indexOf(' ');
        System.out.println(s.substring(0, pos));
        s = s.substring(pos + 1);
    }
    System.out.println(s);
}

Madushan Perera · Accepted Answer · 2016-03-18 04:40:41Z

I think this will solve your problem.

public static List<String> getWords(String text) {
    List<String> words = new ArrayList<>();
    BreakIterator breakIterator = BreakIterator.getWordInstance();
    breakIterator.setText(text);
    int lastIndex = breakIterator.first();
    while (BreakIterator.DONE != lastIndex) {
        int firstIndex = lastIndex;
        lastIndex = breakIterator.next();
        if (lastIndex != BreakIterator.DONE && Character.isLetterOrDigit(text.charAt(firstIndex))) {
            words.add(text.substring(firstIndex, lastIndex));
        }
    }

    return words;
}

public static void main(String[] args) {
    String text = "I like         cats";
    List<String> words = getWords(text);
    for (String word : words) {
        System.out.println(word);
    }
}

Output :

I
like
cats

frankelot · Accepted Answer · 2016-03-18 04:48:36Z

What about something like this, its O(N) time complexity: Just use a string builder to create the string as you iterate through your string, add "\n" whenever you find a space

    String word = "I like cats";
    StringBuilder sb = new StringBuilder();
    boolean newLine = true;
    for(int i = 0; i < word.length(); i++) {
        if (word.charAt(i) == ' ') {
            if (newLine) {
                sb.append("\n");
                newLine = false;
            }
        } else {
            newLine = true;
            sb.append(word.charAt(i));
        }
    }

    String result = sb.toString();

EDIT: Fixed the problem mentioned on comments (new line on multiple spaces)

This will result in extra newlines when there are multiple spaces together.

Antony Dao · Accepted Answer · 2016-03-18 04:56:26Z

0

Sorry, I didnot caution you cannot use replaceAll().

This is my other solution:

    String s = "I like   cats";
    Pattern p = Pattern.compile("([\\S])+");
    Matcher m = p.matcher(s);
      while (m.find( )) {
          System.out.println(m.group());
      }

Old solution:

    String s = "I like   cats";
    System.out.println(s.replaceAll("( )+","\n"));

edited Mar 18, 2016 at 4:56

answered Mar 18, 2016 at 4:45

Antony Dao

4252 silver badges14 bronze badges

Comments

EugenSunic · Accepted Answer · 2019-09-12 22:34:40Z

-1

You almost done all job. Just make small addition, and your code will work as you wish:

for (int i = 0; i < length - 1;) {
  j = text.indexOf(" ", i);

  if (i == j) { //if next space after space, skip it
    i = j + 1;
    continue;
  }

  if (j == -1) {
    j = text.length();
  }
  System.out.print("\n" + text.substring(i, j));
  i = j + 1;
}

edited Sep 12, 2019 at 22:34

EugenSunic

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answered Mar 18, 2016 at 5:42

Ken Bekov

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