无法对非静态方法进行静态引用 [英] cannot make a static reference to a non static method

问题描述

到目前为止，我有以下代码：

So far I have the following code:

import java.util.Scanner;

public class HallLanceMemoryCalculator {
private double currentValue;

public static int displayMenu(){

    Scanner input=new Scanner(System.in);

    int choice=0;

    while(choice<1||choice>5){      
    System.out.println("1.Add");
    System.out.println("2.Subtract");
    System.out.println("3.Multiply");
    System.out.println("4.Divide");
    System.out.println("5.Clear");

    System.out.println("What would you like to do?");
    choice=input.nextInt();
    }
    return choice;
}

public static double getOperand(String prompt){
    Scanner input=new Scanner(System.in);
    System.out.println("What is the second number?");
    double secondNumber=input.nextDouble();
    return secondNumber;
}

public  double getCurrentValue(){
    return currentValue;
}

public void add(double operand2){
    currentValue+=operand2;
}

public void subtract(double operand2){
    currentValue-=operand2;
}

public void multiply(double operand2){
    currentValue*=operand2;
}

public void divide(double operand2){
    currentValue/=operand2;
}

public void clear(){
    currentValue=0;
}

public static void main(String[] args) {
    double value=getCurrentValue(); 
}

}

当我尝试在最后设置double value = getCurrentValue（）; 时，我收到一条错误消息无法对非静态方法进行静态引用。它说修复是使 getCurrentValue（）方法也是静态的，但我被告知不要让我的教授将该字段设为静态。有没有一个简单的解决方案，我只是缺少？

When I try to set double value=getCurrentValue(); at the end, I get an error message "Cannot make a static reference to the non-static method." It says the fix is to make the getCurrentValue() method static as well, but I was told not to make that field static by my professor. Is there a simple solution to this that I am just missing?

推荐答案

静态方法属于类，非静态方法属于该类的实例。

A static method belongs to the class, a non-static method belongs to an instance of the class.

当您调用 getCurrentValue（）时从 main ，您收到错误，因为 main 与任何实例都没有关联。

When you call getCurrentValue() from main, you get an error because main isn't associated with any instance.

你需要创建一个类的实例：

You need to create an instance of the class:

HallLanceMemoryCalculator me = new HallLanceMemoryCalculator();

然后你可以调用实例的 getCurrentValue（）：

Then you can call the instance's getCurrentValue():

double value = me.getCurrentValue();

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