Java String class methods
现在不推荐使用 StringTokenizer 类。建议使用 String 类的 split（）方法或 regex（正则表达式）。
String charAt() method
String compareTo() method
String concat() method
String contains() method
String endsWith() method
String equals() method
String equalsIgnoreCase() method
String format() method
String getBytes() method
String getChars() method
String indexOf() method
String intern() method
String isEmpty() method
String join() method
String lastIndexOf() method
String length() method
String replace() method
String replaceAll() method
String split() method
String startsWith() method
String substring() method
String toCharArray() method
String toLowerCase() method
String toUpperCase() method
String trim() method
String valueOf() method