2016012028+小学四则运算练习软件项目报告

         /**
	 * 产生运算符，个数及种类，并限制种类大于2。此处采用递归
	 * @return int[] ope 返回生成的运算符
	 */
	 private static int[] operator() {
		 Random random = new Random();
		 boolean flag = false;
		 int n=random.nextInt(3)+3;  //3-5个运算符,运算符个数
		 ope=new int[n];
		 for (int j=0;j<n;j++)  ope[j]=random.nextInt(4);  //随机选择某个运算符
		 for (int j = 1; j < n; j++) {               //控制运算符种类
			if(ope[0]!=ope[j]) flag = true;
		 }
		 if (!flag)  {
		   operator();
		 }
		 return ope;
	     }
	    

	  /**
	  * 中缀表达式转化为后缀表达式
	  * @param LinkedList<String> list
	  * @param int n
	  * @param String[] ss
          * @return int m 
	  */
          
  private static int transferToPostfix(LinkedList<String> list,int n,String[] ss){
        Iterator<String> it=list.iterator();
        while (it.hasNext()) {
            String s = it.next();
            if (isOperator(s)) {
                if (operators.isEmpty()) {
                    operators.push(s);
                }
                else {
                    //如果读入的操作符为非")"且优先级比栈顶元素的优先级高或一样，则将操作符压入栈
                    if (priority(operators.peek())<priority(s)&&!s.equals(")")) {
                        operators.push(s);
                    }
                    else if(!s.equals(")")&&priority(operators.peek())>=priority(s)){
                        while (operators.size()!=0&&priority(operators.peek())>=priority(s)&&!operators.peek().equals("(")) {
                            if (!operators.peek().equals("(")) {
                                String operator=operators.pop();
                                sb.append(operator).append(" ");                           
                                output.push(operator);
                            }
                        }
                        operators.push(s);
                    }
                    //如果读入的操作符是")"，则弹出从栈顶开始第一个"("及其之前的所有操作符
                    else if (s.equals(")")) {
                        while (!operators.peek().equals("(")) {
                            String operator=operators.pop();
                            sb.append(operator).append(" ");
                            output.push(operator);
                        }
                        //弹出"("
                        operators.pop();
                    }
                }
            }
            //读入的为非操作符
            else {
                sb.append(s).append(" ");          	
                output.push(s);
            }
        }
        if (!operators.isEmpty()) {
            Iterator<String> iterator=operators.iterator();
            while (iterator.hasNext()) {
                String operator=iterator.next();
                sb.append(operator).append(" ");
                output.push(operator);
                iterator.remove();
            }
        }
        int m = calculate(n,ss);
        sb.delete(0,sb.length());
        return  m ;
    }

          /**
	  * 计算后缀表达式并输出到文件
	  * @param int n
	  * @param String[] ss
          * @return int n 
	  */	  
	  private static int calculate(int n,String[] ss){
	        LinkedList<String> mList=new LinkedList<>();
	        String[] postStr=sb.toString().split(" ");
	        for (String s:postStr) {
	            if (isOperator(s)){
	                if (!mList.isEmpty()){
	                    int num1=Integer.valueOf(mList.pop());
	                    int num2=Integer.valueOf(mList.pop());
	                    if (s.equals("/")&&(num1==0||num1>num2)){
	                        n--;
	                        return n;
	                    }
	                    if(s.equals("-")&&num2%num1!=0){
	                    	n--;
	                    	return n;
	                    }
	                    int newNum=cal(num2,num1,s);
	                    mList.push(String.valueOf(newNum));
	                }
	            }
	            else {
	                //数字则压入栈中
	                mList.push(s);
	            }
	        }
	        String content = "";
	        if (!mList.isEmpty()){
	        	for (int j = 0; j < ss.length; j++) {
	        		content+=ss[j];
				}
	        	  content+="="+mList.pop()+"\r\n";
	        }
	        
	        if(!file.exists()) file = new File("result.txt");	        
	    	try {
				FileOutputStream fos = new FileOutputStream(file,true);//建立文件流,用以输出计算式	       
				fos.write(content.getBytes());
				fos.flush();
				fos.close();
			} catch (FileNotFoundException e) {
				e.printStackTrace();
			} catch (IOException e) {
				e.printStackTrace();
			}
	        return n;
	    }

 public static void main(String[] args) {
	        Scanner scanner=new Scanner(System.in);
	        int num;
	        num = scanner.nextInt();
	        int n=0;
	        printHeader();
	        while (n<num) {
	        	LinkedList<String> list=new LinkedList<>();
	        	list=new CalCu().expression();
	        	Iterator<String> it=list.iterator();
	        	StringBuilder sd=new StringBuilder();
	            while (it.hasNext()) {               
	               sd.append(it.next()).append(" ");
	            }
	            String[] ss=sd.toString().split(" ");
	            n = transferToPostfix(list,n,ss);
	            n++;
			}
	        System.out.println("输出成功");
	        scanner.close();
	    }