CamelCase Method in Java

The challenge

Write a simple CamelCase method for strings.

All words must have their first letter capitalized without spaces.

Example:

// "HelloCase"
camelCase("hello case");

// "CamelCaseWord"
camelCase("camel case word");

The solution in Java code

Option 1:

public class Solution {

    public static String camelCase(String str) {
        String[] words = str.trim().split("\\s+");
        if (words.length==0) return "";
        StringBuilder sb = new StringBuilder();
      
        for (int i=0; i<words.length; i++) {
            String word = words[i];
            if (word.length()>1) {
              String s = word.substring(0, 1).toUpperCase() + word.substring(1, word.length());
              sb.append(s);
            } else {
              sb.append(word.toUpperCase());
            }
        }
      
        return sb.toString();
    }

}

Option 2:

import java.util.Arrays;
import java.util.stream.Collectors;

public class Solution {

    public static String camelCase(String str) {
        return (str == null || str.isEmpty())?"":Arrays.stream(str.trim().split("\\s+"))
                .map(s -> s.substring(0,1).toUpperCase()+s.substring(1,s.length()))
                .collect(Collectors.joining());
    }

}

Option 3:

import org.apache.commons.lang3.text.WordUtils;

public class Solution {

    public static String camelCase(String str) {
      String result = ""; 
      for(String s : str.trim().split(" ")){
        result += WordUtils.capitalize(s);
      }
      return result;    
    }

}

Test cases to validate our solution

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;

public class SolutionTest {

    @Test
    public void testTwoWords() {
        assertEquals("TestCase", Solution.camelCase("test case"));
    }

    @Test
    public void testThreeWords() {
        assertEquals("CamelCaseMethod", Solution.camelCase("camel case method"));
    }

    @Test
    public void testLeadingSpace() {
        assertEquals("CamelCaseWord", Solution.camelCase(" camel case word"));
    }

    @Test
    public void testTrailingSpace() {
        assertEquals("SayHello", Solution.camelCase("say hello "));
    }

    @Test
    public void testSingleLetter() {
        assertEquals("Z", Solution.camelCase("z"));
    }

    @Test
    public void testTwoSpacesBetweenWords() {
        assertEquals("AbC", Solution.camelCase("ab  c"));
    }

    @Test
    public void testEmptyString() {
        assertEquals("", Solution.camelCase(""));
    }
    
}
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