我写的Java学生成绩管理系统源代码(13) if(mp.containsKey( String.valueOf(deleteNumber).toString())) { mp.remove(deleteNumber); }else throw new NumberNotFoundException(); Collection c = mp.values(); Iterator iter = c.iterator(); while(iter.hasNext()) { s1 = (String)iter.next(); s3 +=s1+"\n"; } BufferedReader in2 = new BufferedReader( new StringReader(s3)); PrintWriter out = new PrintWriter( new BufferedWriter(