//正则表达式
"(\\b[a-z@H_403_3@][A-Za-z@H_403_3@]*\\b)"

测试用例

Matcher mac = Pattern.compile("(\\b[a-z@H_403_3@][a-zA-Z@H_403_3@]*\\b)").matcher("the  Aalone await abc wait success sdf");
 while (mac.find()) {@H_403_3@
 System.out.println(mac.group());@H_403_3@

 }@H_403_3@

输出

看到将所有小写开头的单词都输出来了

the@H_403_3@
await
abc
wait@H_403_3@
success
sdf