なんか構造が美しくないのでリファクタしたい・・

StringUtils.java

public class StringUtils {

	private static final char NO_BREAK_SPACE           = '\u00A0';
	private static final char NARROW_NOBREAK_SPACE     = '\u202F';
	private static final char ZERO_WIDTH_NOBREAK_SPACE = '\uFEFF';
	private static final char WORD_JOINER              = '\u2060';
	private static final char FIGURE_SPACE             = '\u2007';
	
	public static boolean isSpace(char c) {
		
		if (Character.isWhitespace(c)) {
			return true;
		}
		
		// isWhitespace()で判定できない空白文字
		switch (c) {
		case NO_BREAK_SPACE:
		case NARROW_NOBREAK_SPACE:
		case ZERO_WIDTH_NOBREAK_SPACE:
		case WORD_JOINER:
		case FIGURE_SPACE:
			return true;
		}
		
		return false;
	}
	
	public static CharSequence trim(CharSequence str) {
		
		if (str == null) {
			return null;
		}
		
		int len = str.length();
		int head = 0, tail = len -1;
		
		for (; head < len && isSpace(str.charAt(head)); head++);
		if (head == len) {
			return "";
		}
		
		for (; tail >= 0 && isSpace(str.charAt(tail)); tail--);
		
		return (head == 0 && tail == len -1) ? str : str.subSequence(head, tail + 1);
	}

	
	public static List<String> tokenize(String str) {

		ArrayList<String> tokens = new ArrayList<String>();
		if (str == null || str.length() == 0) {
			return tokens;
		}

		int i = 0;
		char[] chars = str.toCharArray();
		while (true) {

			while (i < chars.length && isSpace(chars[i])) {
				i++;
			}
			if (i >= chars.length) {
				break;
			}

			StringBuilder buffer = new StringBuilder();
			if (chars[i] == '"') {
				i++; // SkipDQ
				while (i < chars.length && chars[i] != '"') {
					buffer.append(chars[i++]);
				}
				i++; // SkipDQ
			} else {
				while (i < chars.length && !isSpace(chars[i])) {
					buffer.append(chars[i++]);
				}
			}

			if (buffer.length() > 0) {
				String token = trim(buffer).toString();
				if (!token.isEmpty()) {
					tokens.add(token);
				}
			}

		}

		return tokens;

	}	
}

StringUtilsTest.java

	@Test
	public void トークン分割テスト_1() {
		
		List<String> tokens = StringUtils.tokenize(null);
		assertThat(tokens.size(), is(0));
		
	}
	
	@Test
	public void トークン分割テスト_2() {
		
		List<String> tokens = StringUtils.tokenize("");
		assertThat(tokens.size(), is(0));
		
	}
	
	@Test
	public void トークン分割テスト_3() {
		
		List<String> tokens = StringUtils.tokenize("あ");
		assertThat(tokens.size(), is(1));
		assertThat(tokens.get(0), is("あ"));
		
	}
	
	@Test
	public void トークン分割テスト_4() {
		
		List<String> tokens = StringUtils.tokenize("　あ　");
		assertThat(tokens.size(), is(1));
		assertThat(tokens.get(0), is("あ"));
		
	}
	
	@Test
	public void トークン分割テスト_5() {
		
		List<String> tokens = StringUtils.tokenize(" あ ");
		assertThat(tokens.size(), is(1));
		assertThat(tokens.get(0), is("あ"));
		
	}
	
	@Test
	public void トークン分割テスト_6() {
		
		List<String> tokens = StringUtils.tokenize(" あ い ");
		assertThat(tokens.size(), is(2));
		assertThat(tokens.get(0), is("あ"));
		assertThat(tokens.get(1), is("い"));
		
	}
	
	@Test
	public void トークン分割テスト_7() {
		
		List<String> tokens = StringUtils.tokenize(" \"あ い ");
		assertThat(tokens.size(), is(1));
		assertThat(tokens.get(0), is("あ い"));
		
	}
	
	@Test
	public void トークン分割テスト_8() {
		
		List<String> tokens = StringUtils.tokenize(" \"あ い   \" う　え　お ");
		assertThat(tokens.size(), is(4));
		assertThat(tokens.get(0), is("あ い"));
		assertThat(tokens.get(1), is("う"));
		assertThat(tokens.get(2), is("え"));
		assertThat(tokens.get(3), is("お"));
		
	}
	
	@Test
	public void トークン分割テスト_9() {
		
		List<String> tokens = StringUtils.tokenize(" \"あ い   \" う　え　お \"");
		assertThat(tokens.size(), is(4));
		assertThat(tokens.get(0), is("あ い"));
		assertThat(tokens.get(1), is("う"));
		assertThat(tokens.get(2), is("え"));
		assertThat(tokens.get(3), is("お"));
		
	}
	
	@Test
	public void トークン分割テスト_10() {
		
		List<String> tokens = StringUtils.tokenize(" \"あ い う　え　お \"");
		assertThat(tokens.size(), is(1));
		assertThat(tokens.get(0), is("あ い う　え　お"));
		
	}
	
	@Test
	public void トークン分割テスト_11() {
		
		List<String> tokens = StringUtils.tokenize(" \"   あ い う　え　お \"   ");
		assertThat(tokens.size(), is(1));
		assertThat(tokens.get(0), is("あ い う　え　お"));
		
	}
	
	@Test
	public void トークン分割テスト_12() {
		
		List<String> tokens = StringUtils.tokenize(" \"あ い う　え　お\"\"");
		assertThat(tokens.size(), is(1));
		assertThat(tokens.get(0), is("あ い う　え　お"));
		
	}

	@Test
	public void トークン分割テスト_13() {
		
		List<String> tokens = StringUtils.tokenize(" \"あ い う　え　お\"\"  ");
		assertThat(tokens.size(), is(1));
		assertThat(tokens.get(0), is("あ い う　え　お"));
		
	}

小宮氏のをいったんコピペでもってきた

処理を追加していったら衰退してしまった・・。