java - 计算具有运算符优先级的过程

Question

我正在尝试计算一个算术表达式，该表达式以字符串形式输入(例如，( 5+4*5-1/8 )，结果为 3)。我输入一个表达式并将其转换为数组。第一的;结果将从第一个元素开始，并且会在循环中发生变化。但问题是运算符优先级。如何在循环中使用运算符存在？这是我的代码:

import java.util.Scanner;


public class HesapMakinesi {

    private char value[];

    private int count;

    private Scanner str = new Scanner(System.in);

    private String process;

    HesapMakinesi() {

        System.out.print("Enter the process ");

        process = str.next();

        //System.out.println(islem);

        Initializer(process);

    }

    private void Initializer(String process) {

        count = process.toCharArray().length;

        value = new char [count];

        int i;

        System.arraycopy(process.toCharArray(), 0, value, 0, count);

        //System.out.println(value);

        if(value[0]=='-' || value[0]=='+' || value[0]=='/' || value[0]=='*' ||  // A process cannot start with an operator
                value[count-1]=='-' || value[count-1]=='+' || value[count-1]=='/' || value[count-1]=='*') {

            System.out.println("You have entered a wrong process.Please enter again!!!");

            System.out.print("Enter the process: ");

            process = str.next();

            Initializer(process);

        }



        for(i=0; i<count; i++) { // A process cannot include a character except operators

            if( value[i]!='+' && value[i]!='-' && value[i]!='*' && value[i]!='/' && value[i]!='(' && value[i]!=')' && !Character.isDigit(value[i]) ) {

                System.out.println("You have entered a wrong process.Please enter again!!!");

                System.out.print("Enter the process: ");

                process = str.next();

                Initializer(process);

            }


        }


        for(i=0; i<count-1; i++) { // A process cannot have operators sequantially

            if( !Character.isDigit(value[i]) && !Character.isDigit(value[i+1]) ) {

                if( (value[i] == '+' && value[i+1] == '+' ) || (value[i] == '+' && value[i+1] == '-' ) || (value[i] == '+' && value[i+1] == '*' ) || 
                        (value[i] == '+' && value[i+1] == '/' ) ) {

                    System.out.println("You have entered a wrong process.Please enter again!!!");

                    System.out.print("Enter the process: ");

                    process = str.next();

                    Initializer(process);

                }

                else if( (value[i] == '-' && value[i+1] == '+' ) || (value[i] == '-' && value[i+1] == '-' ) || (value[i] == '-' && value[i+1] == '*' ) || 
                        (value[i] == '-' && value[i+1] == '/' ) ) {

                    System.out.println("You have entered a wrong process.Please enter again!!!");

                    System.out.print("Enter the process: ");

                    process = str.next();

                    Initializer(process);

                }

                else if( (value[i] == '*' && value[i+1] == '+' ) || (value[i] == '*' && value[i+1] == '-' ) || (value[i] == '*' && value[i+1] == '*' ) || 
                        (value[i] == '*' && value[i+1] == '/' ) ) {

                    System.out.println("You have entered a wrong process.Please enter again!!!");

                    System.out.print("Enter the process: ");

                    process = str.next();

                    Initializer(process);

                }

                else if( (value[i] == '/' && value[i+1] == '+' ) || (value[i] == '/' && value[i+1] == '-' ) || (value[i] == '/' && value[i+1] == '*' ) || 
                        (value[i] == '/' && value[i+1] == '/' ) ) {

                    System.out.println("You have entered a wrong process.Please enter again!!!");

                    System.out.print("Enter the process: ");

                    process = str.next();

                    Initializer(process);

                }


            }

        }

        //sCount();

    }

    /*private void Count(){

        double result,temp;

        int i;

        for(i=0; i<count; i++) {

            if( value[i]!= )

        }


    }*/

}

Answer 1

你不是这样做的。您需要在评估表达式之前对其进行解析。我建议您阅读Shunting-yard algorithm .