用Java中的另一个类制作数组对象

Question

Firstly, let me preface this by saying that I'm quite new to Java, so apologies if I mess up on any terminology or anything.

Now, secondly, on to my question.

I've made a String array in one class('Warranty'):

public class Warranty {

private int monthnum;
private String[] partscovered = new String[5]; {

    partscovered[0]= "Engine";
    partscovered[1]= "Mirrors";
    partscovered[2]= "Electrics";
    partscovered[3]= "Body";
    partscovered[4]= "Wheels";

}


  public Warranty(int monthnum,String[] partscovered) {

    this.monthnum = monthnum;
    this.partscovered= partscovered;

}



public void displaywarranty() {

    System.out.println("*******");
    System.out.println(8);
    System.out.println(partscovered);
    System.out.println("\n");

}

I'm trying to instantiate it in another class('VehicleTest'):

public class VehicleTest {

    public static void main(String[] args) {

         ......

        Warranty warranty = new Warranty(0,partscovered); //returns an error: 'partscovered cannot be resolved to a variable'
        warranty.displaywarranty();

          }


}

I want to print the array to the console of my IDE, but I'm a little stuck as to why I'm getting the above error message (ie partscovered cannot be resolved to a variable ). It seems to me as if I've done it right, but clearly I haven't so I'm a little stumped to be honest. Any help would be greatly appreciated! :)

Answer 1

There are three problems with this code.

Firstly, the way to print an array is

System.out.println(Arrays.toString(partscovered));

Secondly, you cannot pass partscovered to the Warrenty constructor because partscovered is a field of Warranty . You would have to make a separate variable. Something like

String[] pc = {"Steering Wheel", "Exhaust Pipe"};
Warranty warranty = new Warranty(0, pc);
warranty.displaywarranty();

Alternatively, you could avoid using a variable at all

Warranty warranty = new Warranty(0, new String[]{"Steering Wheel", "Exhaust Pipe"});

Finally, I personally dislike your use of an instance initializer to fill up the array partscovered with "Engine" , "Mirrors" etc. This happens even if you pass an array to the constructor. Another way to provide a default array is to write a second constructor:

private String[] partscovered; // This is deliberately not assigned

public Warranty(int monthnum) {
    this.monthnum = monthnum;
    this.partscovered = new String[]{"Engine", "Mirrors", "Electrics", "Body", "Wheels"};
}

public Warranty(int monthnum,String[] partscovered) {
    this.monthnum = monthnum;
    this.partscovered = partscovered;
}