简单的Java计算器

Question

首先，这不是一门功课的问题。我正在练习关于java的知识。我认为一个很好的方法就是在没有帮助的情况下写一个简单的程序。不幸的是，我的编译器告诉我错误，我不知道如何解决。在不改变逻辑和代码的情况下，有人能够指出我的一些错误在哪里？由于

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

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); 


    } 
} 

这将工作

Answer 2

operands和operators超出范围主。你在构造函数中声明了局部变量，所以当你退出ctor时，他们有资格获得GC并离开。

你有编译错误 - 他们的10。

Answer 3

你的主要方法需要声明如下：

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

而且，好像你只提供一个参数传送给所有的算术方法（加，减等），但它们需要两个。

public int addition(int x, int y); 

不能与addition(operands)被调用，也就是只有一个参数，该参数是错误的类型（该方法需要两个int，你给它一个Scanner）。所有这些方法都是一样的。你需要从Scanner提取int秒。你可以用Scanner.nextInt()来做到这一点。

Answer 4

的另一个问题是，该行

y = operands.next(); 

试图广场Scanner.next()一个String返回到被声明为类型int的一个变量y。

Scanner.nextInt()该方法可用于试图返回int。

Answer 5

除了其他的答案，你的main（）方法必须是为了一个程序入口点静态。在main（）中，你需要构造你自己的Calculator对象，并调用它的方法。

Answer 6

就像提示一样，开始将

import java.util.*;

扔到程序中通常不是一个好主意，因为它会使程序不必要的大而慢。所有你需要的是

import java.util.Scanner;

如果我是正确的，那么大多数如果不是java.lang中的所有东西都已经为你导入了。

Answer 7

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 8

这是所有伟大的，但您使用的编写Java程序是什么？ 也许你应该考虑使用像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）它还会告诉你程序的问题是'英文'。 另外，还要考虑这个类的，也许做一个计算器的更容易，更复杂的方式：

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!"); 
} 

}
而作为习惯问题，而不是做：

import java.util.*; 

它是更好要做：

import java.util.Scanner; 

这可能不会有很大的区别，但如果您正在运行一个更大的程序导入整个java.util会大大减慢你的程序。

希望这会有所帮助！

Answer 9

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 10

您正在要求用户键入整数，但是您将语句operands.next();作为输入。尽量保持与你的变量和用户输入保持一致，所以把它改为operands.nextInt()会有帮助。