字符串应满足要求：
1.它由一些用空格分隔的单词组成。
2.每个单词中只允许字母、数字、下划线、'和"
3.每个单词必须以字母或引号开头
现在我写了这个，它不符合最后的要求：
public boolean test(String string) {
return string.matches("[A-Za-z0-9_' \"]+");
}
如果我给出一个非法字符串 "this world start with 123digit" ，它会返回 false，但它会返回 true：
public boolean test("there is a word start with 123digit"){
\\my previous code return true.
\\so someone PLEASE HELP to implement the method so
\\ it will return false in such situation.
}
也是这种情况，它应该返回false：
public boolean test("there is a word start with _underscore"){
\\my previous code return true.
\\so someone PLEASE HELP to implement the method so
\\ it will return false in such situation.
}