求帮忙看下这段代码为什么有时候会生成一个空的字符串添加到stl集合里？

Question

public void testSort3(){

String string = "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYabcdefghijklmnopqrstuvwxyz";

List<String> stl = new ArrayList<String>();

Random random = new Random();

for(int j = 0;j < 10;j++){

char e;

String st = "";

for(int i = 0;i < random.nextInt(string.length());i++){

//判断stl是否包含上一个生成的字符串，如果为true，

//则重新循环生成，如果为false，则添加到stl

do{

e = string.charAt(random.nextInt(string.length()));

st = st + e;

}while(stl.contains(st));

}

stl.add(st);

}

System.out.println("----------排序前---------");

for (String string2 : stl) {

System.out.println("字符串："+string2);

}

Collections.sort(stl);

System.out.println("----------排序后---------");

for (String string2 : stl) {

System.out.println("字符串："+string2);

}

}

输出结果：

----------排序前---------

字符串：1YeO69qEpz

字符串：Ox8EHbOcmmunkF

字符串：GajsKoNIq79

字符串：LJJwdreXtL4hr

字符串：YAxE

字符串：VtpRe0MFa

字符串：62pxdYnYuGI9jObYphtDH

字符串：

字符串：dWR02Q

字符串：KavtY2r

----------排序后---------

字符串：

字符串：1YeO69qEpz

字符串：62pxdYnYuGI9jObYphtDH

字符串：GajsKoNIq79

字符串：KavtY2r

字符串：LJJwdreXtL4hr

字符串：Ox8EHbOcmmunkF

字符串：VtpRe0MFa

字符串：YAxE

字符串：dWR02Q

Answer 1

XAPTVLUKTDTBJMRNJHXMDGMOQUDNXAKNQZVIYJSVKGDMJMPFPZVSZKHNWMPYCLOCMVVXNWFPFOXTDWFUDAPYODBEHXARHXHRZWYXMIZIYUEMKAHQZWLUKNPTPZFPZVLCYAKUGCEBEURGWTPFOXNJGJZBYAAQSVYVLUKNVUQTJMVEUQGDFUQZKTCYZPZSUJYBXBXGWZTOXBYODNUDAAWQAUOFWSCIEUPMJMWZBFTIKHDNJEAWMPBORTDUXZPMVKOKFIYUKUKILHYVEBENPSPLUEAWGJZBEBJFUKOKFIKBKTXFORVYPEPSBDLBEHYTPFIMVEHCYOEHRHVYUYUXNEGWZMPEUKAQEAXUZPLUKVEHQNPKWUVPJDUTTVZORBUOBCOLSCGFNRFWMDNKYHJROKAJMPMEHXVRIMCSWFHUKNXHXACFBGVEAQAJZVLPCVSJCVHXAEKJLLDDUZKGAKFVBGUBLYBOWWLJZXEXYIUUWSLIPDQAJNNEAGOYOVFUILZWGHNKPWFTGBLPFPMMJSQQOBFJQQVVFPELIVKHUVLCGAMCXYGQPJGJRJGQQHBZTAPYUBWQXSTAXKEHPZJRVFUUOMRHBSKOOSRDDPTFUBJDGQTHVROIROSLUMACCOYJLIZTZQCYZZNCMZVGNIFVLYZVJJDQZSTDNGULERPJRDSVSCATNHMGCTKOUOBECZJNQOFFMVFZUAXUHVNQKUYRHELECSRRLYLJFUEKORGXYQWVAHNNZTXUROECCJZTDRORTFMMTERYYFFPCSJCJATWNDNNULVOBEIPTZFQXHASDGENDTWQQIODXOPOZISTJNNUHRLHAKACSVFVVLIIFMWGFDXVLLJJQVPYCZLPCSTJOTPTIMGWGNWGADLM

Answer 2

因为do-while循环是先执行一次再进行判断，可以改成while循环运行试下看下结果