我使用Java从用户获得一个字符串输入。我试着让输入的第一个字母大写。
我试了一下:
String name;
BufferedReader br = new InputStreamReader(System.in);
String s1 = name.charAt(0).toUppercase());
System.out.println(s1 + name.substring(1));
这导致了以下编译错误:
类型不匹配:不能从InputStreamReader转换为BufferedReader 不能在基本类型char上调用toUppercase()
当前回答
来自Ameen Mahheen的答案很好，但如果我们有一些双空格字符串，如“hello world”，那么sb.append得到IndexOutOfBounds异常。正确的做法是在这行之前测试，做:
private String capitalizer(String word){
String[] words = word.split(" ");
StringBuilder sb = new StringBuilder();
if (words[0].length() > 0) {
sb.append(Character.toUpperCase(words[0].charAt(0)) + words[0].subSequence(1, words[0].length()).toString().toLowerCase());
for (int i = 1; i < words.length; i++) {
sb.append(" ");
if (words[i].length() > 0) sb.append(Character.toUpperCase(words[i].charAt(0)) + words[i].subSequence(1, words[i].length()).toString().toLowerCase());
}
}
return sb.toString();
}
其他回答
字符串首字母大写的更短/更快的版本代码是:
String name = "stackoverflow";
name = name.substring(0,1).toUpperCase() + name.substring(1).toLowerCase();
name的值为Stackoverflow
下面的解决方案将工作。
String A = "stackOverflow";
String ACaps = A.toUpperCase().charAt(0)+A.substring(1,A.length());
//Will print StackOverflow
你不能在原始字符上使用toUpperCase()，但你可以先将整个String变成大写，然后取第一个字符，然后像上面所示的那样追加到子字符串。
public static String capitalizer(final String texto) {
// split words
String[] palavras = texto.split(" ");
StringBuilder sb = new StringBuilder();
// list of word exceptions
List<String> excessoes = new ArrayList<String>(Arrays.asList("de", "da", "das", "do", "dos", "na", "nas", "no", "nos", "a", "e", "o", "em", "com"));
for (String palavra : palavras) {
if (excessoes.contains(palavra.toLowerCase()))
sb.append(palavra.toLowerCase()).append(" ");
else
sb.append(Character.toUpperCase(palavra.charAt(0))).append(palavra.substring(1).toLowerCase()).append(" ");
}
return sb.toString().trim();
}
你可以试试这个
/**
* capitilizeFirst(null) -> ""
* capitilizeFirst("") -> ""
* capitilizeFirst(" ") -> ""
* capitilizeFirst(" df") -> "Df"
* capitilizeFirst("AS") -> "As"
*
* @param str input string
* @return String with the first letter capitalized
*/
public String capitilizeFirst(String str)
{
// assumptions that input parameter is not null is legal, as we use this function in map chain
Function<String, String> capFirst = (String s) -> {
String result = ""; // <-- accumulator
try { result += s.substring(0, 1).toUpperCase(); }
catch (Throwable e) {}
try { result += s.substring(1).toLowerCase(); }
catch (Throwable e) {}
return result;
};
return Optional.ofNullable(str)
.map(String::trim)
.map(capFirst)
.orElse("");
}
您可以使用以下代码:
public static void main(String[] args) {
capitalizeFirstLetter("java");
capitalizeFirstLetter("java developer");
}
public static void capitalizeFirstLetter(String text) {
StringBuilder str = new StringBuilder();
String[] tokens = text.split("\\s");// Can be space,comma or hyphen
for (String token : tokens) {
str.append(Character.toUpperCase(token.charAt(0))).append(token.substring(1)).append(" ");
}
str.toString().trim(); // Trim trailing space
System.out.println(str);
}
