简单的Java计算器

Question

首先，这不是一个家庭作业问题。我正在练习我的java知识。我认为做到这一点的一个好方法是在没有帮助的情况下编写一个简单的程序。不幸的是，我的编译器告诉我错误，我不知道如何修复。在不改变太多逻辑和代码的情况下，有人可以指出我的一些错误在哪里吗？谢谢

import java.lang.*;
import java.util.*;

public class Calculator
{
    private int solution;
    private int x;
    private int y;
    private char operators;

    public Calculator()
    {
        solution = 0;
        Scanner operators = new Scanner(System.in);
        Scanner operands = new Scanner(System.in);
    }

    public int addition(int x, int y)
    {
       return x + y;
    }
    public int subtraction(int x, int y)
    {
       return x - y;
    }
    public int multiplication(int x, int y)
    {    
       return x * y;
    }
    public int division(int x, int y)
    {
       solution = x / y;
       return solution;
    }
    public void main (String[] args)
    {
      System.out.println("What operation? ('+', '-', '*', '/')"); 

      System.out.println("Insert 2 numbers to be subtracted");
       System.out.println("operand 1: ");
       x = operands;
       System.out.println("operand 2: ");
       y = operands.next();
      switch(operators)
      {
          case('+'):
            addition(operands);
            operands.next();
            break;
          case('-'):
            subtraction(operands);
            operands.next();
            break;
          case('*'):
            multiplication(operands);
            operands.next();
            break;
          case('/'):
            division(operands);
            operands.next();
            break;
       }
  }
}

Answer 1

这一切都很棒，但是你用什么程序来编写你的java呢？
也许您应该考虑使用像 Eclipse 这样的 IDE，因为它可以自动检测错误并添加导入。 （我不确定你的是否这样做）它还告诉你你的程序的问题是什么“英语”。
另外，考虑这个类可能是一种更简单、更简单的计算器方法：

public class Calculator {
public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    System.out.print("Enter an Operator: ");
    String in = sc.next();
    char oper = in.charAt(0);

    System.out.print("Enter a number: ");
    in = sc.next();
    double num1 = Double.parseDouble(in);

    System.out.print("Enter another number: ");
    in = sc.next();
    double num2 = Double.parseDouble(in);

    if(oper == '+') {
        double result = num1 + num2;
        System.out.println(result);
    } else if(oper == '-') {
        double result = num1 - num2;
        System.out.println(result);
    } else if(oper == 'x') {
        double result = num1 * num2;
        System.out.println(result);
    } else if(oper == '/') {
        double result = num1 / num2;
        System.out.println(result);
    } else {
        double result = num1 % num2;
        System.out.println(result);
    }
        System.out.println("Hope this helped your mathmatical troubles!");
}

}
作为一个习惯问题，与其这样做：

import java.util.*;

不如这样做：

import java.util.Scanner;

这在这里可能没有多大区别，但是如果您正在运行一个更大的程序，导入整个 java.util 将大大减慢您的速度程序。

希望这有帮助！

Answer 2

您的主要方法需要这样声明：

public static void main(String[] args) {..}

此外，您似乎只为所有算术方法（加法、减法等）提供一个参数，尽管它们需要两个。

public int addition(int x, int y);

不能用addition(operands)调用，即只有一个参数，并且参数的类型错误（该方法需要两个int，你给它一个<代码>扫描仪）。所有这些方法都是如此。您需要从 Scanner 中提取 int。您可以使用 Scanner.nextInt() 来做到这一点。

Answer 3

import java.lang.*;

import java.util.*;


public class Calculator
{
    private int solution;
    private int x;
    private int y;
 private char operators;

    public Calculator()
    {
        solution = 0;
        Scanner operators = new Scanner(System.in);
        Scanner operands = new Scanner(System.in);
    }

    public int addition(int x, int y)
    {
       return x + y;
    }
    public int subtraction(int x, int y)
    {
       return x - y;
    }
    public int multiplication(int x, int y)
    {    
       return x * y;
    }
    public int division(int x, int y)
    {
       solution = x / y;
       return solution;
    }
    public void main (String[] args)
    {
      System.out.println("What operation? ('+', '-', '*', '/')"); 

      System.out.println("Insert 2 numbers to be subtracted");
       System.out.println("operand 1: ");
       x = operands;
       System.out.println("operand 2: ");
       y = operands.next();
      switch(operators)
      {
          case('+'):
            addition(operands);
            operands.next();
            break;
          case('-'):
            subtraction(operands);
            operands.next();
            break;
          case('*'):
            multiplication(operands);
            operands.next();
            break;
          case('/'):
            division(operands);
            operands.next();
            break;
       }
  }
}

Answer 4

您要求用户输入整数，但您将语句 operands.next(); 作为输入。尝试与变量和用户输入保持一致，因此将其更改为 operands.nextInt() 会有所帮助。

Answer 5

作为提示，开始投掷通常不是一个好主意

import java.util.*;

into your program because it makes the program unnecessarily large and slow. All you need for this is to

import java.util.Scanner;

If I'm correct, most if not everything in java.lang is already imported for you.

Answer 6

package org.com;

import java.lang.*; 
import java.util.*; 

public class Calculator 
{ 
    private int solution; 
    private static int x; 
    private static int y; 
    private char operators; 

    public Calculator() 
    { 
        solution = 0; 
        Scanner operators = new Scanner(System.in); 
        Scanner operands = new Scanner(System.in); 
    } 

    public int addition(int x, int y) 
    { 
       return x + y; 
    } 
    public int subtraction(int x, int y) 
    { 
       return x - y; 
    } 
    public int multiplication(int x, int y) 
    {     
       return x * y; 
    } 
    public int division(int x, int y) 
    { 
       solution = x / y; 
       return solution; 
    } 

    public void calc(int ops){
         x = 4; 
         System.out.println("operand 2: "); 
         y = 5; 

         switch(ops) 
         { 
             case(1): 
               System.out.println(addition(x, y)); 

           //    operands.next(); 
               break; 
             case(2): 
                 System.out.println(subtraction(x, y)); 
              // operands.next(); 
               break; 
             case(3): 
                 System.out.println(multiplication(x, y)); 
             //  operands.next(); 
               break; 
             case(4): 
                 System.out.println(division(x, y));
             //  operands.next(); 
               break; 
          } 
    }
    public static void main (String[] args) 
    { 
      System.out.println("What operation? ('+', '-', '*', '/')");  
      System.out.println(" Enter 1 for Addition");
      System.out.println(" Enter 2 for Subtraction");
      System.out.println(" Enter 3 for Multiplication");
      System.out.println(" Enter 4 for Division");

       Calculator calc = new Calculator();
       calc.calc(1);


  } 
} 

这会起作用

Answer 7

操作数和运算符超出了main的范围。您在构造函数中声明局部变量，因此当您退出构造函数时，它们有资格进行 GC 并且消失。

您有编译错误 - 其中 10 个。

Answer 8

另一个问题是，该行

y = operands.next();

尝试放置从 String。 html#next()" rel="nofollow noreferrer">Scanner.next() 到声明为类型 的变量 y 中int。

Scanner.nextInt( ) 方法可用于尝试返回 int。

Answer 9

package com.abc;

import java.util.Scanner;

public class Calculator {
    private static final String pos = "+";
    private static final String neg = "-";
    private static final String mult = "*";
    private static final String div = "/";

    private enum operation {
        pos, neg, mult, div
    };
    private int solution;
    private int x;
    public int getX() {
        return x;
    }

    public void setX(int x) {
        this.x = x;
    }

    public int getY() {
        return y;
    }

    public void setY(int y) {
        this.y = y;
    }

    private int y;



    static Scanner operators;

    public Calculator() {
        solution = 0;
        operators = new Scanner(System.in);

    }

    public int addition(int x, int y) {
        return x + y;
    }

    public int subtraction(int x, int y) {
        return x - y;
    }

    public int multiplication(int x, int y) {
        return x * y;
    }

    public int division(int x, int y) {
        solution = x / y;
        return solution;
    }

    public static void main(String[] args) {
        Calculator calc = new Calculator();

        System.out.println("Insert 2 numbers");

        System.out.println("operand 1: ");

        calc.setX(Integer.parseInt(operators.next()));

        System.out.println("operand 2: ");
        calc.setY(Integer.parseInt(operators.next()));

        System.out.println("What operation? ('pos', 'neg', 'mult', 'div')");
        operation ttt = operation.valueOf(operators.next());
        int output = 0 ;
        switch(ttt){
        case pos:
            output = calc.addition(calc.getX(), calc.getY());

            break;
          case neg:
              output = calc.subtraction(calc.getX(), calc.getY());

            break;
          case mult:
              output = calc.multiplication(calc.getX(), calc.getY());

            break;
          case div:
              output = calc.division(calc.getX(), calc.getY());

            break;
        }
        System.out.println("output ="+output);
    }
}

Answer 10

除了其他答案之外，您的 main() 方法必须是静态的才能成为程序入口点。在 main() 中，您需要构造自己的 Calculator 对象，并调用该对象的方法。