如何访问数组方法中的参数？ 爪哇

Question

Just trying to understand the basics of how this should work. Here is my code.---------------------------> This is my main class.

public class Driver
{
    public static void main(String[] args)
    {
        //create new instance of the ArrayLab class with parameter of 10
        ArrayLab array = new ArrayLab(10);

        //search for 2
        array.search(2);
    }
}

The class ArrayLab has a method assigned to it called search with parameter of (2). So far this is what I have.

import java.util.Arrays;
public class ArrayLab
{
    //array instance variable
    int[] array1 = new int[10];

    //array constructor
    public ArrayLab(int integer)
    {
        //class parameter = 10
        int[] array1 = new int[integer];

    }

//method
public void search(int integer)
    {
        int[] array1= new int[]{integer};
        System.out.println(Arrays.toString(array1));
    }
}

So the big question is what am I doing right? or wrong? I realize this is probably pretty basic, just struggling to understand what is happening inside the code. Thanks :)

Answer 1

Your Driver class is good.

So, lets take one line at a time

int[] array1 = new int[10];

Okay, you made a public int array of size 10, more precisely [0, 0, 0, 0, 0, 0, 0, 0, 0, 0] .

public ArrayLab(int integer)
{
    int[] array1 = new int[integer];
}

This is called a constructor. You are passing in integer , and making a new array called array1 which is local to this scope, therefore different than the one before. This array1 contains integer -many zeros.

To use and initialize the previous array1 , change your code up to here to this

int[] array1;
public ArrayLab(int integer)
{
    this.array1 = new int[integer];
}

Next,

public void search(int integer)
    {
        int[] array1= new int[]{integer};
    }
}

This, again, creates a new array, but only one value. So say integer was 2, then [2] .

Answer 2

I don't know what the purpose of your ArrayLab class is , but here are some problems

1. In the constructor you are initializing a local array1 not your instance variable .

2. search method is doing nothing but again initializing a local array1 .

Answer 3

Alright, so whats happening is in your class Driver your creating a object of your class ArrayLab. You send this class a constructor which creates a local variable array1. Your search class initializing another local array1 this is what i would do for your ArrayLab class

import java.util.Arrays;
public class ArrayLab
{
    int[] array1;

    //array constructor
    public ArrayLab(int integer)
    {
        this.array1 = new int[integer];

    }

//method
public void search(int integer)
    {
        System.out.println(array1[integer]);
    }
}