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  • mini dc课堂练习补交

    实验截图

    实验代码

    import java.util.StringTokenizer;
    import java.util.Stack;
    
    public class MyDC {
        /**
         * constant for addition symbol
         */
        private final char ADD = '+';
        /**
         * constant for subtraction symbol
         */
        private final char SUBTRACT = '-';
        /**
         * constant for multiplication symbol
         */
        private final char MULTIPLY = '*';
        /**
         * constant for division symbol
         */
        private final char DIVIDE = '/';
        /**
         * the stack
         */
        private Stack<Integer> stack;
    
        public MyDC() {
            stack = new Stack<Integer>();
        }
    
        public int evaluate(String expr) {
            int op1, op2, result = 0;
            String token;
            StringTokenizer tokenizer = new StringTokenizer(expr);
    
            while (tokenizer.hasMoreTokens()) {
                token = tokenizer.nextToken();
    
                //如果是运算符,调用isOperator
                if (isOperator(token)) {
                    op2=(stack.pop()).intValue();//从栈中弹出操作数2
                    op1=(stack.pop()).intValue();//从栈中弹出操作数1
                    result=evalSingleOp(token.charAt(0),op1,op2);//根据运算符和两个操作数调用evalSingleOp计算result;
                    stack.push(new Integer(result));//计算result入栈;
                } else//如果是操作数
                stack.push(new Integer(Integer.parseInt(token)));//操作数入栈;
            }
    
            return result;
        }
    
        private boolean isOperator(String token) {
            return (token.equals("+") || token.equals("-") ||
                    token.equals("*") || token.equals("/"));
        }
    
        private int evalSingleOp(char operation, int op1, int op2) {
            int result = 0;
    
            switch (operation) {
                case ADD:
                    result = op1 + op2;
                    break;
                case SUBTRACT:
                    result = op1 - op2;
                    break;
                case MULTIPLY:
                    result = op1 * op2;
                    break;
                case DIVIDE:
                    result = op1 / op2;
            }
    
            return result;
        }
    }
    

    代码链接

    练习总结

    • 1、对于isOperator()的调用不够明确。
    • 2、计算中间结果的代码为result=evalSingleOp(token.charAt(0),op1,op2);
    • 3、操作数入栈需进行强制类型转换Integer.parseInt(token)
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  • 原文地址:https://www.cnblogs.com/LeeX1997/p/6802495.html
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