【ACM模式】队列操作

求解代码publicstaticvoidmain(String[]args)throwsIOException{BufferedReaderbrnewBufferedReader(newInputStreamReader(System.in));StreamTokenizerinnewStreamTokenizer(br);PrintWriteroutnewPrintWriter(newOutputStreamWriter(System.out));DequeIntegerqueuenewArrayDeque();while(in.nextToken()!StreamTokenizer.TT_EOF){intn(int)in.nval;for(inti0;in;i){in.nextToken();inta(int)in.nval;switch(a){case1:in.nextToken();queue.add((int)in.nval);break;case2:if(queue.isEmpty()){out.println(ERR_CANNOT_POP);}else{queue.pollFirst();}break;case3:if(queue.isEmpty()){out.println(ERR_CANNOT_QUERY);}else{out.println(queue.peekFirst());}break;case4:out.println(queue.size());break;default:break;}}}out.flush();out.close();}