关于创建类数组的困惑

Question

Suppose I have two classes in a Java Package:

Class1.java and Class2.java

So, if in Class1.java , I do the following:

public Class2[] QR;

public static int x = 10;

Then later on somewhere in the code:

QR = new Class2[x];

So basically, I will be passing value 10 to class2 , right? Please correct me if I have not understood it properly.

Answer 1

QR = new Class2[x];

这将创建一个大小为10的Class2数组。

Answer 2

No you are not passing 10 to the value of class2. You are making an array of class2 whose size is 10.

Detail explaination:

public Class2[] QR;

In this statement you are saying, Hey i want to hold some objects of Class2 in an array whose name is QR. (Till now you have not specified how many objects you want to keep in QR, so initialization of array is not done yet)

QR = new Class2[x];

Here you are saying, now i know how many (x many items) objects i will keep in QR, so allocate memory( via new keyword) to QR.

So basically you have just initialized the array with the number of items you will keep in array, ie you have specified the size of array.

Now class2 object will reside at some index in the QR (index 0 to 9). Class2 c = QR[0]; // for example

Answer 3

You can create an array of Class2 and initialize it as:

public Class2[] QR;  // Declare the array
public static int x = 10;
QR = new Class2[x];  // Allocate for 10 instances memory 

// Now create the and init the instances
for (int i=0 ; i<QR.lenght ; i++) {
   QR[i] = new Class2();  // Call the constructor
}