JAVA 一个字符串"xxxxabcabc" 如何去掉字符串前四个xxxx是四个不固定字符，保留abcabc,菜鸟求助！谢谢

String str = "xxxxabcabc";
// 去掉前四个字符
str = str.substring(4);
// 判断是否以stay开头
boolean flg = str.startWith("stay");

String a ="xxxxabcabc";
a=a.substring(4,a.length())

String b ="stayACZCZCZC";
if("stay".equle(b.substring(0,4))

String str = "stayACZCZCZC";
str = str.substring(4, str.length());
System.out.println(str);

String s ="xxxxabcabc";

System.out.println(s.substring(4, s.length()));

String s1 = "stayACZCZCZC";

String flag = s1.substring(0, 4);

if(flag.equals("stay")){
System.out.println("yes");
}else{
System.out.println("no");
}

String a = "stayACZCZCZC";

//问题一
System.out.println(a.replaceAll(a.substring(0,4),""));
System.out.println("----------------------------");
//问题二
if("stay".equals(a.substring(0, 4))){
System.out.println("ok");
}else{
System.out.println("ng");
}