简单的java计算器错误

Question

您好，我前两天对 java 产生了兴趣，在看一些教程时，在看到一个超级简单的加法计算示例完成后，我决定制作一个计算器。我想知道我哪里出错了。请帮助我对它超级陌生。（如果有影响的话，我也使用 eclipse idk）

import java.util.Scanner;

public class calculator {
public static void main(String args[]){
    Scanner operation = new Scanner(System.in);
    Scanner number = new Scanner(System.in);
    int x;
    int y;
    int problem = multiplication, division, addition, subtraction;
    int answer = answerM, answerD, answerA, answerS;


    System.out.println("enter first number: "); 
    x = number.nextInt();
    System.out.println("enter operator: "); 
    signs(); = operation.nextInt();     
    System.out.println("enter second number: ");
    y = number.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;
                }
            }
        }
    }
}
private static int signs() {
    multiplication = "*";
    division = "/";
    addition = "+";
    subtraction = "-";
    return 0;
}
}

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)

Answer 1

这几行有问题

signs(); = operation.nextInt(); 

if (problem = signs()){

它将signs()的返回值分配给变量problem。

您可以更好地使用equals() 即problem.equals(signs())

Answer 2

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，加法是你写的字符串

int problem = multiplication, division, addition, subtraction;

• problem 是 int，multiplication 是 string，所以这种转换是不可能的。
• 这个方法的返回类型是int，它总是返回0，所以需要返回类型为int。它必须是无效的（这不是问题，而是最佳实践）

Answer 3

问题在于这两行：

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

您已经声明了int problem = multiplication，但没有在任何地方定义乘法。 同样，在声明中int answer = answerM 也没有定义。

您可以通过声明这两个 int 变量来消除这些错误：

int answerM = 0;
int multiplication = 0;

Answer 4

检查此代码.. 这工作正常。检查您的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;
  //    }
  }