下面是这个问题的Kotlin版本:

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()
}

我使用wordUppercase(String s)从雨滴库。 因为这是我的库，这里只有一个方法

 /**
  * 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);
 }

希望能有所帮助。

worddutil .capitalize(str) (from apache common -text)

(注意:如果你需要“fOO BAr”变成“fOO BAr”，那么用大写的(..)代替)

String s="hi dude i                                 want apple";
    s = s.replaceAll("\\s+"," ");
    String[] split = s.split(" ");
    s="";
    for (int i = 0; i < split.length; i++) {
        split[i]=Character.toUpperCase(split[i].charAt(0))+split[i].substring(1);
        s+=split[i]+" ";
        System.out.println(split[i]);
    }
    System.out.println(s);

1. Java 8流

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(" "));
}

例子:

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

对于foo bAR到foo bAR，替换map()方法如下:

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

2. 字符串()(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));
}

例子:

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文本

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

titlecase:

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

有关详细信息，请查看本教程。

我只想通过仅使用Java代码为该问题添加一个替代解决方案。 没有额外的库

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();
        }