Exception in thread "main" java.lang.NullPointerException

Question

public class Good {
// Good类
    private String name;
    private double price;

    public Good(String name, double price) {
        this.name = name;
        this.price = price;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

public class Goodgl {
//Goodgl 类
     Good [] good1  =new Good[10];
    {
        good1[index]= new Good("海天酱油",1.5);
        good1[++index]= new Good("山西陈醋",5.4);
    }

  static int index=0;
   // 显示商品
    public void xian(){
        for (int i = 0; i <good1.length ; i++) {
           // System.out.println(good1[0]);
            if(good1[i]!=null){
                System.out.println((i+1)+" "+good1[i].getName()+good1[i].getPrice());
            }
        }
    }
    //添加商品
    public void  add(String name,double price) {
        System.out.println(index);
        for (int i = 0; i <good1.length ; i++) {
            if(good1[i]==null){
                good1[i].setName(name);//!!!!!!!!这行添加商品的功能报错,Exception in thread "main" java.lang.NullPointerException
                good1[i].setPrice(price);
                System.out.println(good1[i].getName());
                break;
            }

        }
     }
    }

//测试类
public class Test1 {
    public static void main(String[] args) {
        Goodgl goodgl=new Goodgl();
        Scanner input=new Scanner(System.in);
        fn:while (true){
            System.out.println("欢迎光临商品信息管理系统");
            System.out.println("1.查看全部商品信息");
            System.out.println("2,添加商品信息");
            System.out.println("3.根据商品名称查看商品价格");
            System.out.print("请选择操作");
            int number=input.nextInt();
            switch (number){
                case 1:
                    System.out.println("商品信息显示");
                    System.out.println("序号"+'\t'+"商品名称"+'\t'+"商品价格");
                    goodgl.xian();
                    System.out.print("是否继续操作");
                    String cao=input.next();
                    if(cao.equals("y")){
                        continue;
                    }else {
                        System.out.println("谢谢使用本系统,欢迎下次光临");
                        break fn;
                    }
                case 2:
                    System.out.println("商品信息添加");
                    System.out.print("请输入商品名称");
                    String name=input.next();
                    System.out.print("请输入商品价格");
                    double price=input.nextDouble();
                    goodgl.add(name,price);

                    System.out.println("商品添加成功");
                    System.out.print("是否继续操作");
                    String cao1=input.next();
                    if(cao1.equals("y")){
                        continue;
                    }else {
                        System.out.println("谢谢使用本系统,欢迎下次光临");
                        break fn;
                    }
            }
        }
    }
}

//如何使我这个添加商品的功能不报错,且能正常添加一个商品

Answer 1

import java.util.Scanner;

public class Good {
    private String name;
    private double price;

    public Good(String name, double price) {
        this.name = name;
        this.price = price;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

public class Goodgl {
    private Good[] goods;
    private int index;

    public Goodgl() {
        goods = new Good[10];
        index = 0;
        goods[index] = new Good("海天酱油", 1.5);
        goods[++index] = new Good("山西陈醋", 5.4);
    }

    public void xian() {
        for (int i = 0; i < goods.length; i++) {
            if (goods[i] != null) {
                System.out.println((i + 1) + " " + goods[i].getName() + " " + goods[i].getPrice());
            }
        }
    }

    public void add(String name, double price) {
        if (index < goods.length) {
            goods[index] = new Good(name, price);
            index++;
            System.out.println("商品添加成功");
        } else {
            System.out.println("商品列表已满，无法添加更多商品");
        }
    }
}

public class Test1 {
    public static void main(String[] args) {
        Goodgl goodgl = new Goodgl();
        Scanner input = new Scanner(System.in);

        fn: while (true) {
            System.out.println("欢迎光临商品信息管理系统");
            System.out.println("1.查看全部商品信息");
            System.out.println("2.添加商品信息");
            System.out.println("3.根据商品名称查看商品价格");
            System.out.print("请选择操作");
            int number = input.nextInt();

            switch (number) {
                case 1:
                    System.out.println("商品信息显示");
                    System.out.println("序号\t商品名称\t商品价格");
                    goodgl.xian();
                    System.out.print("是否继续操作");
                    String cao = input.next();
                    if (cao.equals("y")) {
                        continue;
                    } else {
                        System.out.println("谢谢使用本系统，欢迎下次光临");
                        break fn;
                    }
                case 2:
                    System.out.println("商品信息添加");
                    System.out.print("请输入商品名称");
                    String name = input.next();
                    System.out.print("请输入商品价格");
                    double price = input.nextDouble();
                    goodgl.add(name, price);
                    System.out.print("是否继续操作");
                    String cao1 = input.next();
                    if (cao1.equals("y")) {
                        continue;
                    } else {
                        System.out.println("谢谢使用本系统，欢迎下次光临");
                        break fn;
                    }
            }
        }
    }
}