求解代码publicstaticvoidmain(String[]args)throwsIOException{BufferedReaderbrnewBufferedReader(newInputStreamReader(System.in));StreamTokenizerinnewStreamTokenizer(br);PrintWriteroutnewPrintWriter(newOutputStreamWriter(System.out));DequeIntegerstacknewArrayDeque();in.nextToken();intn(int)in.nval;for(inti0;in;i){in.nextToken();Stringstr(String)in.sval;switch(str){casepush:in.nextToken();stack.push((int)in.nval);break;casepop:if(stack.isEmpty()){out.println(Empty);}else{stack.pop();}break;casequery:if(stack.isEmpty()){out.println(Empty);}else{out.println(stack.peek());}break;casesize:out.println(stack.size());break;default:break;}}out.flush();out.close();}小贴士官方文档明确标注Deque接口及其实现类如ArrayDeque应优先于Stack类使用。