string

    判定前缀

    boolean startsWith
    (String
    prefix)    		 Tests if this string starts with the specified prefix.
    boolean startsWith
    (String
    prefix, int toffset)    		 Tests if the substring of this string beginning at the specified index starts with the specified prefix.

    截取串

    String substring
    (int beginIndex)    		 Returns a string that is a substring of this string.
    String substring
    (int beginIndex, int endIndex)    		 Returns a string that is a substring of this string.

    截取字符

    char charAt
    (int index)    		 Returns the char value at the specified index.

    字符串转化为字符数组

    char[] toCharArray
    ()    		 Converts this string to a new character array.