使用Split方法将字符串拆分为单词，然后使用内置的字符串函数将每个单词大写，然后附加在一起。

伪代码(ish)

string = "the sentence you want to apply caps to";
words = string.split(" ") 
string = ""
for(String w: words)

//This line is an easy way to capitalize a word
    word = word.toUpperCase().replace(word.substring(1), word.substring(1).toLowerCase())

    string += word

最后字符串看起来像这样 "你想要加大写字母的句子"

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
}

  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);
    }
}

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。

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);
    }
}));

这是我做的另一种方法

    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);