BufferedReader br = new BufferedReader(new InputStreamReader(System.in));   

System.out.println("Enter the sentence : ");

try
{
    String str = br.readLine();
    char[] str1 = new char[str.length()];

    for(int i=0; i<str.length(); i++)
    {
        str1[i] = Character.toLowerCase(str.charAt(i));
    }

    str1[0] = Character.toUpperCase(str1[0]);
    for(int i=0;i<str.length();i++)
    {
        if(str1[i] == ' ')
        {                   
            str1[i+1] =  Character.toUpperCase(str1[i+1]);
        }
        System.out.print(str1[i]);
    }
}
catch(Exception e)
{
    System.err.println("Error: " + e.getMessage());
}

如果你只担心第一个单词的首字母大写:

private String capitalize(final String line) {
   return Character.toUpperCase(line.charAt(0)) + line.substring(1);
}

我使用下面的函数。我认为它在性能上更快。

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();
}

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();
    }
}

这里是RxJava解决方案的问题

    String title = "this is a title";
    StringBuilder stringBuilder = new StringBuilder();
    Observable.fromArray(title.trim().split("\\s"))
        .map(word -> word.substring(0, 1).toUpperCase() + word.substring(1).toLowerCase())
        .toList()
        .map(wordList -> {
            for (String word : wordList) {
                stringBuilder.append(word).append(" ");
            }
            return stringBuilder.toString();
        })
        .subscribe(result -> System.out.println(result));

不过我还不喜欢for循环。

//如此简单和基本

public void capalizedFirstCharOne(String str){
    char[] charArray=str.toCharArray();
    charArray[0]=Character.toUpperCase(charArray[0]);
    for(int i=1;i<charArray.length;i++){
        if(charArray[i]==' ' ){
            charArray[i+1]=Character.toUpperCase(charArray[i+1]);
        }
    }

    String result=new String(charArray);
    System.out.println(result);
}