有很多方法可以转换第一个大写单词的第一个字母。我有个主意。这很简单:

public String capitalize(String str){

     /* The first thing we do is remove whitespace from string */
     String c = str.replaceAll("\\s+", " ");
     String s = c.trim();
     String l = "";

     for(int i = 0; i < s.length(); i++){
          if(i == 0){                              /* Uppercase the first letter in strings */
              l += s.toUpperCase().charAt(i);
              i++;                                 /* To i = i + 1 because we don't need to add               
                                                    value i = 0 into string l */
          }

          l += s.charAt(i);

          if(s.charAt(i) == 32){                   /* If we meet whitespace (32 in ASCII Code is whitespace) */
              l += s.toUpperCase().charAt(i+1);    /* Uppercase the letter after whitespace */
              i++;                                 /* Yo i = i + 1 because we don't need to add
                                                   value whitespace into string l */
          }        
     }
     return l;
}

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

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()
}

这是另一种表达方式:

private String capitalize(String line)
{
    StringTokenizer token =new StringTokenizer(line);
    String CapLine="";
    while(token.hasMoreTokens())
    {
        String tok = token.nextToken().toString();
        CapLine += Character.toUpperCase(tok.charAt(0))+ tok.substring(1)+" ";        
    }
    return CapLine.substring(0,CapLine.length()-1);
}

String toBeCapped = "i want this sentence capitalized";

String[] tokens = toBeCapped.split("\\s");
toBeCapped = "";

for(int i = 0; i < tokens.length; i++){
    char capLetter = Character.toUpperCase(tokens[i].charAt(0));
    toBeCapped +=  " " + capLetter + tokens[i].substring(1);
}
toBeCapped = toBeCapped.trim();

package corejava.string.intern;

import java.io.DataInputStream;

import java.util.ArrayList;

/*
 * wap to accept only 3 sentences and convert first character of each word into upper case
 */

public class Accept3Lines_FirstCharUppercase {

    static String line;
    static String words[];
    static ArrayList<String> list=new ArrayList<String>();

    /**
     * @param args
     */
    public static void main(String[] args) throws java.lang.Exception{

        DataInputStream read=new DataInputStream(System.in);
        System.out.println("Enter only three sentences");
        int i=0;
        while((line=read.readLine())!=null){
            method(line);       //main logic of the code
            if((i++)==2){
                break;
            }
        }
        display();
        System.out.println("\n End of the program");

    }

    /*
     * this will display all the elements in an array
     */
    public static void display(){
        for(String display:list){
            System.out.println(display);
        }
    }

    /*
     * this divide the line of string into words 
     * and first char of the each word is converted to upper case
     * and to an array list
     */
    public static void method(String lineParam){
        words=line.split("\\s");
        for(String s:words){
            String result=s.substring(0,1).toUpperCase()+s.substring(1);
            list.add(result);
        }
    }

}