如何将java中字符串中每个单词的第一个和最后一个字母大写

Question

How to capitalize the first and last letters of every word in a string

i have done it this way -

    String cap = "";
    for (int i = 0; i < sent.length() - 1; i++)
    {
        if (sent.charAt(i + 1) == ' ')
        {
            cap += Character.toUpperCase(sent.charAt(i)) + " " + Character.toUpperCase(sent.charAt(i + 2));
            i += 2;
        }
        else
            cap += sent.charAt(i);
    }
    cap += Character.toUpperCase(sent.charAt(sent.length() - 1));
    System.out.print (cap);

It does not work when the first word is of more than single character

Please use simple functions as i am a beginner

Answer 1

Using apache commons lang library it becomes very easy to do:

    String testString = "this string is needed to be 1st and 2nd letter-uppercased for each word";

    testString = WordUtils.capitalize(testString);
    testString = StringUtils.reverse(testString);
    testString = WordUtils.capitalize(testString);
    testString = StringUtils.reverse(testString);
    System.out.println(testString);

ThiS StrinG IS NeedeD TO BE 1sT AnD 2nD Letter-uppercaseD FoR EacH WorD

Answer 2

You should rather split your String with a whitespace as character separator, then for each token apply toUpperCase() on the first and the last character and create a new String as result.

Very simple sample :

  String cap = "";
  String sent = "hello  world. again.";

  String[] token = sent.split("\\s+|\\.$");

  for (String currentToken : token){
      String firstChar = String.valueOf(Character.toUpperCase(currentToken.charAt(0)));
      String between = currentToken.substring(1, currentToken.length()-1);
      String LastChar = String.valueOf(Character.toUpperCase(currentToken.charAt(currentToken.length()-1)));
      if (!cap.equals("")){
        cap += " ";
      }
      cap += firstChar+between+LastChar; 
  }

Of course you should favor the use of StringBuilder over String as you perform many concatenations.

Output result : HellO World. AgaiN HellO World. AgaiN

Answer 3

Your code is missing out the first letter of the first word. I would treat this as a special case, ie

cap = ""+Character.toUpperCase(sent.charAt(0));
for (int i = 1; i < sent.length() - 1; i++)
{
.....

Of course, there are much easier ways to do what you are doing.

Answer 4

Basically you just need to iterate over all characters and replace them if one of the following conditions is true:

• it's the first character
• it's the last character
• the previous character was a whitespace (or whatever you want, eg punctuation - see below)
• the next character is a whitespace (or whatever you want, eg punctuation - see below)

If you use a StringBuilder for performance and memory reasons (don't create a String in every iteration which += would do) it could look like this:

StringBuilder sb = new StringBuilder( "some words    in a list   even with    longer    whitespace in between" );
for( int i = 0; i < sb.length(); i++ ) {
  if( i == 0 || //rule 1
      i == (sb.length() - 1 ) || //rule 2
      Character.isWhitespace( sb.charAt( i - 1 ) ) || //rule 3
      Character.isWhitespace( sb.charAt( i + 1 ) ) ) { //rule 4
    sb.setCharAt( i, Character.toUpperCase( sb.charAt( i ) ) );
  }
}

Result: SomE WordS IN A LisT EveN WitH LongeR WhitespacE IN BetweeN

If you want to check for other rules as well (eg punctuation etc.) you could create a method that you call for the previous and next character and which checks for the required properties.

Answer 5

String stringToSearch = "this string is needed to be first and last letter uppercased for each word";

    // First letter upper case using regex
Pattern firstLetterPtn = Pattern.compile("(\\b[a-z]{1})+");
Matcher m = firstLetterPtn.matcher(stringToSearch);
StringBuffer sb = new StringBuffer();
while(m.find()){
    m.appendReplacement(sb,m.group().toUpperCase()); 
}
m.appendTail(sb);
stringToSearch = sb.toString();
sb.setLength(0);

    // Last letter upper case using regex
Pattern LastLetterPtn = Pattern.compile("([a-z]{1}\\b)+");
m = LastLetterPtn.matcher(stringToSearch);
while(m.find()){
    m.appendReplacement(sb,m.group().toUpperCase()); 
}
m.appendTail(sb);
System.out.println(sb.toString());

output:

ThiS StrinG IS NeedeD TO BE FirsT AnD LasT LetteR UppercaseD FoR EacH WorD