package com.test;

 /**
   * @author Prasanth Pillai
   * @date 01-Feb-2012
   * @description : Below is the test class details
   * 
   * inputs a String from a user. Expect the String to contain spaces and    alphanumeric     characters only.
   * capitalizes all first letters of the words in the given String.
   * preserves all other characters (including spaces) in the String.
   * displays the result to the user.
   * 
   * Approach : I have followed a simple approach. However there are many string    utilities available 
   * for the same purpose. Example : WordUtils.capitalize(str) (from apache commons-lang)
   *
   */
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;

  public class Test {

public static void main(String[] args) throws IOException{
    System.out.println("Input String :\n");
    InputStreamReader converter = new InputStreamReader(System.in);
    BufferedReader in = new BufferedReader(converter);
    String inputString = in.readLine();
    int length = inputString.length();
    StringBuffer newStr = new StringBuffer(0);
    int i = 0;
    int k = 0;
    /* This is a simple approach
     * step 1: scan through the input string
     * step 2: capitalize the first letter of each word in string
     * The integer k, is used as a value to determine whether the 
     * letter is the first letter in each word in the string.
     */

    while( i < length){
        if (Character.isLetter(inputString.charAt(i))){
            if ( k == 0){
            newStr = newStr.append(Character.toUpperCase(inputString.charAt(i)));
            k = 2;
            }//this else loop is to avoid repeatation of the first letter in output string 
            else {
            newStr = newStr.append(inputString.charAt(i));
            }
        } // for the letters which are not first letter, simply append to the output string. 
        else {
            newStr = newStr.append(inputString.charAt(i));
            k=0;
        }
        i+=1;           
    }
    System.out.println("new String ->"+newStr);
    }
}

如果你需要大写标题，这可能很有用。它将每个由" "分隔的子字符串大写，除了"a"或"the"之类的指定字符串。我还没有运行它，因为已经晚了，不过应该没问题。一次使用Apache Commons StringUtils.join()。如果你愿意，你可以用一个简单的循环来代替它。

private static String capitalize(String string) {
    if (string == null) return null;
    String[] wordArray = string.split(" "); // Split string to analyze word by word.
    int i = 0;
lowercase:
    for (String word : wordArray) {
        if (word != wordArray[0]) { // First word always in capital
            String [] lowercaseWords = {"a", "an", "as", "and", "although", "at", "because", "but", "by", "for", "in", "nor", "of", "on", "or", "so", "the", "to", "up", "yet"};
            for (String word2 : lowercaseWords) {
                if (word.equals(word2)) {
                    wordArray[i] = word;
                    i++;
                    continue lowercase;
                }
            }
        }
        char[] characterArray = word.toCharArray();
        characterArray[0] = Character.toTitleCase(characterArray[0]);
        wordArray[i] = new String(characterArray);
        i++;
    }
    return StringUtils.join(wordArray, " "); // Re-join string
}

如果你更喜欢番石榴……

String myString = ...;

String capWords = Joiner.on(' ').join(Iterables.transform(Splitter.on(' ').omitEmptyStrings().split(myString), new Function<String, String>() {
    public String apply(String input) {
        return Character.toUpperCase(input.charAt(0)) + input.substring(1);
    }
}));

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);

我在Java 8中编写了一个更具可读性的解决方案。

public String firstLetterCapitalWithSingleSpace(final String words) {
    return Stream.of(words.trim().split("\\s"))
    .filter(word -> word.length() > 0)
    .map(word -> word.substring(0, 1).toUpperCase() + word.substring(1))
    .collect(Collectors.joining(" "));
}

这个解决方案的要点可以在这里找到:https://gist.github.com/Hylke1982/166a792313c5e2df9d31

这是我的解决方案。

今晚我偶然发现了这个问题，并决定研究一下。我发现Neelam Singh的答案几乎在那里，所以我决定解决这个问题(断在空字符串上)，导致系统崩溃。

您正在寻找的方法名为capString(String s)。 它把“这里才早上5点”变成了“这里才早上5点”。

代码注释得很好，喜欢吧。

package com.lincolnwdaniel.interactivestory.model;

    public class StringS {

    /**
     * @param s is a string of any length, ideally only one word
     * @return a capitalized string.
     * only the first letter of the string is made to uppercase
     */
    public static String capSingleWord(String s) {
        if(s.isEmpty() || s.length()<2) {
            return Character.toUpperCase(s.charAt(0))+"";
        } 
        else {
            return Character.toUpperCase(s.charAt(0)) + s.substring(1);
        }
    }

    /**
     *
     * @param s is a string of any length
     * @return a title cased string.
     * All first letter of each word is made to uppercase
     */
    public static String capString(String s) {
        // Check if the string is empty, if it is, return it immediately
        if(s.isEmpty()){
            return s;
        }

        // Split string on space and create array of words
        String[] arr = s.split(" ");
        // Create a string buffer to hold the new capitalized string
        StringBuffer sb = new StringBuffer();

        // Check if the array is empty (would be caused by the passage of s as an empty string [i.g "" or " "],
        // If it is, return the original string immediately
        if( arr.length < 1 ){
            return s;
        }

        for (int i = 0; i < arr.length; i++) {
            sb.append(Character.toUpperCase(arr[i].charAt(0)))
                    .append(arr[i].substring(1)).append(" ");
        }
        return sb.toString().trim();
    }
}