java - java中的公共(public)变量？

Question

我的程序中有四个类，其中一个包含 main()但是 fruit、ch 和 demand 变量的前三行有错误。我想在每个类中使用这些变量。

    import java.util.Scanner;


public static int fruit = 0;
public static int ch;
public static boolean demand = false;

    class stock{
        synchronized int getfruit(){
            while(demand){
                try{
                    wait();
                }catch(InterruptedException e){
                    System.out.println("Wait fruits uploading");
                }

                System.out.println("cutomer got : " + ch);
                demand = true;
                notify();
            }
            return ch;
        }

        synchronized void putfruits(int ch){
            while(!demand){
                try{
                    wait();
                }catch(InterruptedException e){
                    System.out.println("uploaded already");
                }
                System.out.println("Uploading your demand : "+ ch + "  fruits");
                demand = false;
                notify();
            }
        }
    }
    class vendor implements Runnable{

        stock obj;
        public vendor(stock obj) {
            // TODO Auto-generated constructor stub
        this.obj = obj;
        new Thread(this, "vendor").start();
        }
        @Override
        public void run() {
            // TODO Auto-generated method stub
            obj.putfruits(ch);
        }

    }

    class customer implements Runnable {

        stock obj;
        public customer(stock obj) {
            // TODO Auto-generated constructor stub
        this.obj = obj;
        new Thread(this, "cutomer").start();
        }
        @Override
        public void run() {
            // TODO Auto-generated method stub
            obj.getfruit();
        }

    }
    public class Fruitmarket {
    public static void main (String args[]){
    stock obj2 = new stock();
    System.out.println("Initially market no capacity");
    System.out.println("Enter how much quantity you want ?");
    Scanner in = new Scanner ( System.in);
    ch = in.nextInt();

}
}

我该怎么做？我是 Java 初学者？

Answer 1

这段代码不会编译。您需要将这些变量放在类中，如下所示:

import java.util.Scanner;


class stock {

    public static int fruit = 0;
    public static int ch;
    public static boolean demand = false;

    ....

如果你想在外部访问这些变量，你可以像这样引用它:stock.fruit