学java报错说arr[i]为null

Question

初学java,为什么把中间的t直接用arr[i]代替会报错，说arr[i]为null

```java
javanbean
package test3;

public class car {
     private String brand;
     private int price;
     private String colour;

    public car(String brand, int price, String colour) {
        this.brand = brand;
        this.price = price;
        this.colour = colour;
    }

    public car() {
    }

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public int getPrice() {
        return price;
    }

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

    public String getColour() {
        return colour;
    }

    public void setColour(String colour) {
        this.colour = colour;
    }
}
测试代码
package test3;

import java.util.Scanner;

public class cattest {
    public static void main(String[] args) {
        car[] arr=new car[3];
        Scanner sc=new Scanner(System.in);
        for(int i=0;i<3;i++)
        {
            car t=new car();
            String b=sc.next();
            int c=sc.nextInt();
            String d=sc.next();
            t.setBrand(b);
            t.setPrice(c);
            t.setColour(d);
            arr[i]=t;
        }
        for(int i=0;i<arr.length;i++)
        {
            System.out.println(arr[i].getBrand()+" "+arr[i].getPrice()+" "+arr[i].getColour()+" ");
        }
    }
}

```

Answer 1

那是你语法没写对

    arr[i]=new car();
    String b=sc.next();
    int c=sc.nextInt();
    String d=sc.next();
    arr[i].setBrand(b);
    arr[i].setPrice(c);
    arr[i].setColour(d);

arr只是初始化了一个类型是car的数组，它里面的每一项本身还是null
你需要先给它实例化一个对象
至于中间变量t则是不必要的
-=-=-=-
其实数组和单一对象是一回事
你写car t=new car();那么t就不是null
你写car t，只定义类型而不new，它也是null呀