WordUtils.capitalize(str) (from apache commons-text)

(Note: if you need "fOO BAr" to become "Foo Bar", then use capitalizeFully(..) instead)

The following method converts all the letters into upper/lower case, depending on their position near a space or other special chars.

public static String capitalizeString(String string) {
  char[] chars = string.toLowerCase().toCharArray();
  boolean found = false;
  for (int i = 0; i < chars.length; i++) {
    if (!found && Character.isLetter(chars[i])) {
      chars[i] = Character.toUpperCase(chars[i]);
      found = true;
    } else if (Character.isWhitespace(chars[i]) || chars[i]=='.' || chars[i]=='\'') { // You can add other chars here
      found = false;
    }
  }
  return String.valueOf(chars);
}

From Java 9+

you can use String::replaceAll like this :

public static void upperCaseAllFirstCharacter(String text) {
    String regex = "\\b(.)(.*?)\\b";
    String result = Pattern.compile(regex).matcher(text).replaceAll(
            matche -> matche.group(1).toUpperCase() + matche.group(2)
    );

    System.out.println(result);
}

Example :

upperCaseAllFirstCharacter("hello this is Just a test");

Outputs

Hello This Is Just A Test

I'm using the following function. I think it is faster in performance.

public static String capitalize(String text){
    String c = (text != null)? text.trim() : "";
    String[] words = c.split(" ");
    String result = "";
    for(String w : words){
        result += (w.length() > 1? w.substring(0, 1).toUpperCase(Locale.US) + w.substring(1, w.length()).toLowerCase(Locale.US) : w) + " ";
    }
    return result.trim();
}

1. Java 8 Streams

public static String capitalizeAll(String str) {
    if (str == null || str.isEmpty()) {
        return str;
    }

    return Arrays.stream(str.split("\\s+"))
            .map(t -> t.substring(0, 1).toUpperCase() + t.substring(1))
            .collect(Collectors.joining(" "));
}

Examples:

System.out.println(capitalizeAll("jon skeet")); // Jon Skeet
System.out.println(capitalizeAll("miles o'Brien")); // Miles O'Brien
System.out.println(capitalizeAll("old mcdonald")); // Old Mcdonald
System.out.println(capitalizeAll(null)); // null

For foo bAR to Foo Bar, replace the map() method with the following:

.map(t -> t.substring(0, 1).toUpperCase() + t.substring(1).toLowerCase())

2. String.replaceAll() (Java 9+)

ublic static String capitalizeAll(String str) {
    if (str == null || str.isEmpty()) {
        return str;
    }

    return Pattern.compile("\\b(.)(.*?)\\b")
            .matcher(str)
            .replaceAll(match -> match.group(1).toUpperCase() + match.group(2));
}

Examples:

System.out.println(capitalizeAll("12 ways to learn java")); // 12 Ways To Learn Java
System.out.println(capitalizeAll("i am atta")); // I Am Atta
System.out.println(capitalizeAll(null)); // null

3. Apache Commons Text

System.out.println(WordUtils.capitalize("love is everywhere")); // Love Is Everywhere
System.out.println(WordUtils.capitalize("sky, sky, blue sky!")); // Sky, Sky, Blue Sky!
System.out.println(WordUtils.capitalize(null)); // null

For titlecase:

System.out.println(WordUtils.capitalizeFully("fOO bAR")); // Foo Bar
System.out.println(WordUtils.capitalizeFully("sKy is BLUE!")); // Sky Is Blue!

For details, checkout this tutorial.

Use:

    String text = "jon skeet, miles o'brien, old mcdonald";

    Pattern pattern = Pattern.compile("\\b([a-z])([\\w]*)");
    Matcher matcher = pattern.matcher(text);
    StringBuffer buffer = new StringBuffer();
    while (matcher.find()) {
        matcher.appendReplacement(buffer, matcher.group(1).toUpperCase() + matcher.group(2));
    }
    String capitalized = matcher.appendTail(buffer).toString();
    System.out.println(capitalized);

Here we go for perfect first char capitalization of word

public static void main(String[] args) {
    String input ="my name is ranjan";
    String[] inputArr = input.split(" ");

    for(String word : inputArr) {
        System.out.println(word.substring(0, 1).toUpperCase()+word.substring(1,word.length()));
    }   
}

}

//Output : My Name Is Ranjan

Here is the Kotlin version of the same problem:

fun capitalizeFirstLetterOfEveryWord(text: String): String
{
    if (text.isEmpty() || text.isBlank())
    {
        return ""
    }

    if (text.length == 1)
    {
        return Character.toUpperCase(text[0]).toString()
    }

    val textArray = text.split(" ")
    val stringBuilder = StringBuilder()

    for ((index, item) in textArray.withIndex())
    {
        // If item is empty string, continue to next item
        if (item.isEmpty())
        {
            continue
        }

        stringBuilder
            .append(Character.toUpperCase(item[0]))

        // If the item has only one character then continue to next item because we have already capitalized it.
        if (item.length == 1)
        {
            continue
        }

        for (i in 1 until item.length)
        {
            stringBuilder
                .append(Character.toLowerCase(item[i]))
        }

        if (index < textArray.lastIndex)
        {
            stringBuilder
                .append(" ")
        }
    }

    return stringBuilder.toString()
}

I use wordUppercase(String s) from the Raindrop-Library. Because this is my library, here the single method:

 /**
  * Set set first letter from every word uppercase.
  *
  * @param s - The String wich you want to convert.
  * @return The string where is the first letter of every word uppercase.
  */
 public static String wordUppercase(String s){
   String[] words = s.split(" ");
   for (int i = 0; i < words.length; i++) words[i] = words[i].substring(0, 1).toUpperCase() + words[i].substring(1).toLowerCase();
   return String.join(" ", words);
 }

Hope it helps :)

public void capitaliseFirstLetterOfEachWord()
{
    String value="this will capitalise first character of each word of this string";
    String[] wordSplit=value.split(" ");
    StringBuilder sb=new StringBuilder();

    for (int i=0;i<wordSplit.length;i++){

        sb.append(wordSplit[i].substring(0,1).toUpperCase().
                concat(wordSplit[i].substring(1)).concat(" "));
    }
    System.out.println(sb);
}

this is another way i did

    StringBuilder str=new StringBuilder("pirai sudie test test");

    str.setCharAt(0,Character.toUpperCase(str.charAt(0)));

    for(int i=str.length()-1;i>=0;i--)
    {
        if(Character.isSpaceChar(str.charAt(i)))
            str.setCharAt(i+1,Character.toUpperCase(str.charAt(i+1)));
    }

    System.out.println(str);

I made this little class that can be used to capitilize each word in a sentence. You can change the word separator in the string if this is not a space.

package com.ecnews.ecnews_v01.Helpers;

  public class Capitalize {

  String sentence;
  String separator = " ";

  public Capitalize(String sentence) {
    this.sentence = sentence;
  }

  public void setSeparator(String separator) {
    this.separator = separator;
  }

  public String getCapitalized() {
    StringBuilder capitalized = new StringBuilder("");
    for (String word : sentence.split(separator)) {
        capitalized.append(separator+Character.toUpperCase(word.charAt(0)) + word.substring(1));
    }
    return capitalized.toString().trim();
  }

}

Example:

String sourceName = new Capitalize("this is a test").getCapitalized();

sourceName will be "This Is A Test"

I just want to add an alternative solution for the problem by using only Java code. No extra library

public String Capitalize(String str) {

            String tt = "";
            String tempString = "";
            String tempName = str.trim().toLowerCase();
            String[] tempNameArr = tempName.split(" ");
            System.out.println("The size is " + tempNameArr.length);
            if (tempNameArr.length > 1) {
                for (String t : tempNameArr) {
                    tt += Capitalize(t);
                    tt += " ";
                }
                tempString  = tt;
            } else {
                tempString = tempName.replaceFirst(String.valueOf(tempName.charAt(0)), String.valueOf(tempName.charAt(0)).toUpperCase());
            }
            return tempString.trim();
        }

public static void main(String[] args) throws IOException {
    String words = "this is a test";

    System.out.println(Arrays.asList(words.split(" ")).stream().reduce("",(a, b)->(a + " " + b.substring(0, 1).toUpperCase() + b.substring(1))));


}

}

Heres a lil program I was using to capitalize each first letter word in every subfolder of a parent directory.

private void capitalize(String string)
{
    List<String> delimiters = new ArrayList<>();
    delimiters.add(" ");
    delimiters.add("_");

    File folder = new File(string);
    String name = folder.getName();
    String[] characters = name.split("");

    String newName = "";
    boolean capitalizeNext = false;

    for (int i = 0; i < characters.length; i++)
    {
        String character = characters[i];

        if (capitalizeNext || i == 0)
        {
            newName += character.toUpperCase();
            capitalizeNext = false;
        }
        else
        {
            if (delimiters.contains(character)) capitalizeNext = true;
            newName += character;
        }
    }

    folder.renameTo(new File(folder.getParent() + File.separator + newName));
}

You can also do it very simply like this and preserve any doubled and leading, trailing whitespaces

public static String capitalizeWords(String text) {

    StringBuilder sb = new StringBuilder();
    if(text.length()>0){
        sb.append(Character.toUpperCase(text.charAt(0)));
    }
    for (int i=1; i<text.length(); i++){
        String chPrev = String.valueOf(text.charAt(i-1));
        String ch = String.valueOf(text.charAt(i));

        if(Objects.equals(chPrev, " ")){
            sb.append(ch.toUpperCase());
        }else {
            sb.append(ch);
        }

    }

    return sb.toString();

}