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I needed to port some Coldfusion code to Java that does Title Capitalization on Strings and came up with this solution. I would love it if anyone could give me some pointers as to how to make this more efficient.

import org.apache.commons.text.WordUtils;

import java.util.HashSet;
import java.util.Set;

public class CapFirstTitle 

 public static String CapFirstTitle() 
 String inputText = " from a String to test Title Capitalization CASE hyphenated-word word from IBM od id XX if ";
 Set<String> whiteList = new HashSet<String>();

 whiteList.add("a");
 whiteList.add("above");
 whiteList.add("after");
 whiteList.add("ain't");
 whiteList.add("among");
 whiteList.add("an");
 whiteList.add("and");
 whiteList.add("as");
 whiteList.add("at");
 whiteList.add("below");
 whiteList.add("but");
 whiteList.add("by");
 whiteList.add("can't");
 whiteList.add("don't");
 whiteList.add("for");
 whiteList.add("from");
 whiteList.add("if");
 whiteList.add("in");
 whiteList.add("into");
 whiteList.add("it's");
 whiteList.add("nor");
 whiteList.add("of");
 whiteList.add("off");
 whiteList.add("on");
 whiteList.add("onto");
 whiteList.add("or");
 whiteList.add("over");
 whiteList.add("since");
 whiteList.add("the");
 whiteList.add("to");
 whiteList.add("under");
 whiteList.add("until");
 whiteList.add("up");
 whiteList.add("with");
 whiteList.add("won't");

 Set<String> alwaysCapitalize = new HashSet<String>();
 alwaysCapitalize.add("II");
 alwaysCapitalize.add("III");
 alwaysCapitalize.add("IV");
 alwaysCapitalize.add("V");
 alwaysCapitalize.add("VI");
 alwaysCapitalize.add("VII");
 alwaysCapitalize.add("VIII");
 alwaysCapitalize.add("IX");
 alwaysCapitalize.add("X");
 alwaysCapitalize.add("XI");
 alwaysCapitalize.add("XII");
 alwaysCapitalize.add("XIII");
 alwaysCapitalize.add("XIV");
 alwaysCapitalize.add("XV");
 alwaysCapitalize.add("XVI");
 alwaysCapitalize.add("XVII");
 alwaysCapitalize.add("XVIII");
 alwaysCapitalize.add("XIX");
 alwaysCapitalize.add("XX");
 alwaysCapitalize.add("XXI");
 alwaysCapitalize.add("OD");
 alwaysCapitalize.add("ID");
 alwaysCapitalize.add("PH");
 alwaysCapitalize.add("XH");
 alwaysCapitalize.add("UV");
 alwaysCapitalize.add("DOM");
 alwaysCapitalize.add("GS");

 alwaysCapitalize.add("ii");
 alwaysCapitalize.add("iii");
 alwaysCapitalize.add("iv");
 alwaysCapitalize.add("v");
 alwaysCapitalize.add("vi");
 alwaysCapitalize.add("vii");
 alwaysCapitalize.add("viii");
 alwaysCapitalize.add("ix");
 alwaysCapitalize.add("x");
 alwaysCapitalize.add("xi");
 alwaysCapitalize.add("xii");
 alwaysCapitalize.add("xiii");
 alwaysCapitalize.add("xiv");
 alwaysCapitalize.add("xv");
 alwaysCapitalize.add("xvi");
 alwaysCapitalize.add("xvii");
 alwaysCapitalize.add("xviii");
 alwaysCapitalize.add("xix");
 alwaysCapitalize.add("xx");
 alwaysCapitalize.add("xxi");
 alwaysCapitalize.add("od");
 alwaysCapitalize.add("id");
 alwaysCapitalize.add("ph");
 alwaysCapitalize.add("xh");
 alwaysCapitalize.add("uv");
 alwaysCapitalize.add("dom");
 alwaysCapitalize.add("gs");

 StringBuilder capitalizedString = new StringBuilder();

 if (inputText.contains(" ")) 

 inputText = inputText.toLowerCase().trim();

 String parts = inputText.split(" ");

 for (int i = 0; i < parts.length; i++) i == parts.length - 1) 

 capitalizedString.append(WordUtils.capitalize(parts[i], ' ', '-')).append(" ");

 else 

 if (!whiteList.contains(parts[i])) 

 if (!alwaysCapitalize.contains(parts[i])) 

 capitalizedString.append(WordUtils.capitalize(parts[i], ' ', '-')).append(" ");

 else 

 capitalizedString.append(parts[i].toUpperCase()).append(" ");

 

 else 

 capitalizedString.append(parts[i]).append(" ");

 
 
 
 

 return capitalizedString.toString();
 

• CapFirstTitle() is a method name that disregards java coding conventions for method names. Use standard lowerCamelCase.



• 
  

  whitelist and alwaysCapitalize should be private static final members. You can initialize these in a static initializer block like this:

  
  
  

  private static final Set<String> whitelist = new HashSet<>();
  
  static 
   whitelist.addAll(Arrays.asList("a", "above", "after", ...);
  
  

  
  



• The binary or is a little uncommon in conditions. You won't really get much benefit out of it, especially since the boolean or is short-circuiting. Use || over | here.




• There is a lot of vertical whitespace here. I personally find that hard to follow and I'd delete most of that space if I wrote this code myself.
  YMMV. Since you're extremely consistent about it, I don't see any need to change it.




• You're calling toLowerCase without specifying the Locale. While this may work in most cases, you should be aware of edge-cases involving languages like Turkish. If you have any way to be locale-aware here, you should strive to be. That can save you a lot of headaches down the line :)



• 
  

  This code always appends a " " at the end of the String. You could avoid this by first overwriting the parts array with the capitalized parts and subsequently using Arrays.stream(parts).collect(Collectors.joining(" "));

  
  
  

  Since Java 8, String exposes the method join (thanks to Koekje for pointing that out in the coments), you can use as String.join(" ", parts);

  
  

The last point also contains an option for a deeper rewrite. Consider the following:

String capitalizedParts = Arrays.stream(input.toLowerCase().trim().split(" "))
 .map(CapFirstTitle::capSingleWord)
 .toArray(String::new);
capitalizedParts[0] = WordUtils.capitalize(capitalizedParts[0], ' ', '-');
int lastIdx = capitalizedParts.length - 1;
capitalizedParts[lastIdx] = WordUtils.capitalize(capitalizedParts[lastIdx], ' ', '-');

return String.join(" ", capitalizedParts);

This is a solution that hides the details of whitelist and alwaysCapitalize inside a method and clears the enforced capitalization of the first and last word.

It avoids the (correct, but mental overhead inducing) use of StringBuilder and separates the capitalization logic from the reassembly of the String. You can even go so far and reduce multiple spaces in the same process by filtering out empty array elements in the first Stream.