驼峰命名法(CamelCase)和下划线风格(UnderScoreCase)字符串之间的转换工具类

public class CamelCaseUtils {

private static final char SEPARATOR = '_';

public static String toUnderlineName(String s) {
if (s == null) {
return null;
}

StringBuilder sb = new StringBuilder();
boolean upperCase = false;
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);

boolean nextUpperCase = true;

if (i < (s.length() - 1)) {
nextUpperCase = Character.isUpperCase(s.charAt(i + 1));
}

if ((i >= 0) && Character.isUpperCase(c)) {
if (!upperCase || !nextUpperCase) {
if (i > 0) sb.append(SEPARATOR);
}
upperCase = true;
} else {
upperCase = false;
}

sb.append(Character.toLowerCase(c));
}

return sb.toString();
}

public static String toCamelCase(String s) {
if (s == null) {
return null;
}

s = s.toLowerCase();

StringBuilder sb = new StringBuilder(s.length());
boolean upperCase = false;
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);

if (c == SEPARATOR) {
upperCase = true;
} else if (upperCase) {
sb.append(Character.toUpperCase(c));
upperCase = false;
} else {
sb.append(c);
}
}

return sb.toString();
}

public static String toCapitalizeCamelCase(String s) {
if (s == null) {
return null;
}
s = toCamelCase(s);
return s.substring(0, 1).toUpperCase() + s.substring(1);
}

public static void main(String[] args) {
System.out.println(CamelCaseUtils.toUnderlineName("ISOCertifiedStaff"));
System.out.println(CamelCaseUtils.toUnderlineName("CertifiedStaff"));
System.out.println(CamelCaseUtils.toUnderlineName("UserID"));
System.out.println(CamelCaseUtils.toCamelCase("iso_certified_staff"));
System.out.println(CamelCaseUtils.toCamelCase("certified_staff"));
System.out.println(CamelCaseUtils.toCamelCase("user_id"));
}
}