2016012026+小学四则运算练习软件项目报告

char[] sign = { ‘+‘, ‘-‘, ‘*‘, ‘÷‘};
        // 用数组存运算符
        Random random = new Random();
        int m = random.nextInt(3) + 3;
        //随机生成3-5个运算符数
        int index=(int)(Math.random()* m);
        char a[]=new char[m-1];
        int num[]=new int[5];     
   
        for(int i=0;i<m+1;i++)
          {
            num[i]=(int) ( Math.random() *100 );
            //随机取一百内整数
            for(int j=0;j<m;j++)
            {
                a[j]=sign[index];
                //随机取运算符
            }
            }

 if (m==3)
         {
             System.out.println(num[0]+a[0]+num[1]+a[1]+num[2]+a[2]+num[3]+"="+sum);
         }
         //运算符个数为3时的运算式
         if (m==4)
         {
             
             System.out.println(num[0]+a[0]+num[1]+a[1]+num[2]+a[2]+num[3]+a[3]+
                     num[4]+"="+sum);
         }
        //运算符个数为4时的运算式
         if (m==5)
         {
             System.out.println(num[0]+a[0]+num[1]+a[1]+num[2]+a[2]+num[3]+a[3]+
                     num[4]+a[4]+num[5]+"="+sum);
         }
         //运算符个数为5时的运算式

class PostToResult{
    private String post;   //中缀表达式转换得到的后缀表达式
    private Stack<integer> stack;   //用于得到计算结果的栈

    public PostToResult(String post, Stack<integer> stack) {
        this.post = post;
        this.stack = stack;
    }
 
    //由后缀表达式得到四则运算结果的实现过程
    public void operate(){
        String[] strArr = post.split(" ");
        for(int i = 0; i < strArr.length; i++){
            String temp = strArr[i];
            if(isDigital(temp)){
                stack.push(Integer.valueOf(temp));
            }else{
                int result = compute(temp);
                stack.push(result);
            }
        }
    }
 
    private int compute(String str){
        int re = 0;
        int m = stack.pop();
        int n = stack.pop();
        switch(str){
        case "+" :
            re = n + m;
            break;
        case "-" :
            re = n - m;
            break;
        case "*" :
            re = n * m;
            break;
        case "/" :
            re = n / m;
            break;
        default :
            break;
        }
        return re;
    }
 
    private boolean isDigital(String str){
        char[] chArr = str.toCharArray();
        int len = chArr.length;
        int count = 0;
        for(int i = 0; i < len; i++){
            if(chArr[i] >= ‘0‘ && chArr[i] <= ‘9‘)
                count++;
        }
        return count == len;
    }
 
    public int getResult() {
        return stack.pop();
    }
}