简单java计算器错误

您好，我最近在两天前对java产生了兴趣，在观看一些教程时，在看到一个超级简单的加法计算器示例完成后，我决定制作一个计算器。我在想我在哪里错了。plz help我对它非常陌生。（如果有区别的话，我也会使用EclipseIDK）

错误，错误

Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
    multiplication cannot be resolved to a variable
    answerM cannot be resolved to a variable
    Syntax error on token "=", delete this token
    answerM cannot be resolved to a variable
    Type mismatch: cannot convert from int to boolean

    at calculator.main(calculator.java:10)

这些方面的问题

signs(); = operation.nextInt(); 

它将为变量

问题
分配
符号（）的返回值

您可以更好地使用
equals（）
ie
problem.equals（signs（））
问题1

int problem = multiplication, division, addition, subtraction;

问题2

int answer = answerM, answerD, answerA, answerS;

问题3

signs(); = operation.nextInt();

要记住的事情：

private static int signs() {
    multiplication = "*";
    division = "/";
    addition = "+";
    subtraction = "-";
    return 0;
}

这表明乘法、除法、加法都是你写的字符串

int problem = multiplication, division, addition, subtraction;


问题
是int，而
乘法
是string，因此无法进行此转换
此方法返回类型为int，并且始终返回0，因此返回类型需要为int。它必须为void（这不是问题，而是为了最佳实践）
问题是由以下两条线路引起的：

int problem = multiplication, division, addition, subtraction;
int answer = answerM, answerD, answerA, answerS;

您已经声明了
int problem=multiply
，但乘法没有在任何地方定义。
同样，声明中未定义
int-answerM=answerM

您可以通过声明以下两个int变量来删除这些错误：

int answerM = 0;
int multiplication = 0;

请检查此代码。。这很好用。检查错误并查看解决方案

import java.util.Scanner;

public class calculator {

public static void main(String args[]) {
    // no need of two Scanners to read the same stream
    //   Scanner operation = new Scanner(System.in);
    //  Scanner number = new Scanner(System.in);
    Scanner input = new Scanner(System.in);
    int x;
    int y;
    // can't declare variables like this in java
    //        int problem = multiplication, division, addition, subtraction;
    //        int answer = answerM, answerD, answerA, answerS;
    int answer = 0;

    System.out.println("enter first number: ");
    x = input.nextInt();
    System.out.println("enter operator: ");
    // you can't assign a value to a method call
    //signs(); = operation.nextInt();
    String sign = input.next();
    System.out.println("enter second number: ");
    y = input.nextInt();
    //        System.out.println(answer);


   //        if (problem == signs()) {
   //            answerM = x * y;
   //        } else {
   //            if (problem = signs()) {
  //                answerD = x / y;
  //            } else {
  //                if (problem == signs()) {
  //                    answerA = x + y;
  //                } else {
  //                    if (problem == signs()) {
  //                        answerS = x - y;
  //                    }
  //                }
  //            }
  //        }
    if (sign.equals("*")) {
        answer = x * y;
    } else {
        if (sign.equals("/")) {
            answer = x / y;
        } else {
            if (sign.equals("+")) {
                answer = x + y;
            } else {
                if (sign.equals("-")) {
                    answer = x - y;
                }
            }
        }
    }
    System.out.println(answer);

}
   //This method  always return '0'
  //    private static int signs() {
  //        multiplication = "*";
  //        division = "/";
  //        addition = "+";
  //        subtraction = "-";
  //        return 0;
  //    }
  }

在开始编写计算器之前，请花些时间阅读语言参考资料。像
int problem=乘法、除法、加法、减法之类的语句表示您需要一些读取。@devnull，如果前面声明了一个
乘法，
，它就可以工作了；）问题太多了。从文档开始学习，或者买一本好书，“一边看教程”。我建议你读一些书。YouTube教程遗漏了很多细节。丹尼尔·梁的优秀Java教科书《Java编程入门》。我相信最新的版本是第9版：）很酷，谢谢。我会尝试一下，然后在像这样急匆匆进入之前多读一点java。@user3097986好的，古德……继续：-）哦，好的，我知道我在这一部分错在哪里了。谢谢，伙计，我一定会换的。非常感谢。感谢您分析和解释int x和int y的每个部分，如果它是公共int x；和公众智力；它们在一个方法中。（int main方法）因此它们仅在该方法中可见。把它们公之于众毫无意义。检查问题。
int answerM = 0;
int multiplication = 0;

import java.util.Scanner;

public class calculator {

public static void main(String args[]) {
    // no need of two Scanners to read the same stream
    //   Scanner operation = new Scanner(System.in);
    //  Scanner number = new Scanner(System.in);
    Scanner input = new Scanner(System.in);
    int x;
    int y;
    // can't declare variables like this in java
    //        int problem = multiplication, division, addition, subtraction;
    //        int answer = answerM, answerD, answerA, answerS;
    int answer = 0;

    System.out.println("enter first number: ");
    x = input.nextInt();
    System.out.println("enter operator: ");
    // you can't assign a value to a method call
    //signs(); = operation.nextInt();
    String sign = input.next();
    System.out.println("enter second number: ");
    y = input.nextInt();
    //        System.out.println(answer);


   //        if (problem == signs()) {
   //            answerM = x * y;
   //        } else {
   //            if (problem = signs()) {
  //                answerD = x / y;
  //            } else {
  //                if (problem == signs()) {
  //                    answerA = x + y;
  //                } else {
  //                    if (problem == signs()) {
  //                        answerS = x - y;
  //                    }
  //                }
  //            }
  //        }
    if (sign.equals("*")) {
        answer = x * y;
    } else {
        if (sign.equals("/")) {
            answer = x / y;
        } else {
            if (sign.equals("+")) {
                answer = x + y;
            } else {
                if (sign.equals("-")) {
                    answer = x - y;
                }
            }
        }
    }
    System.out.println(answer);

}
   //This method  always return '0'
  //    private static int signs() {
  //        multiplication = "*";
  //        division = "/";
  //        addition = "+";
  //        subtraction = "-";
  //        return 0;
  //    }
  }