Can we define new Object[3][] without defining number of columns?

问题

Can someone please help me understand the following code? I'm new to java, I'm trying to learn Objects[]. This code compiles but retval does not return anything?

I've done a lot of search online but can't find why is Object[3][] compiles and does not complain?
What does the following code mean?
(new Object[1])[0] = tt;

How can "retval[0] = new Object[1];" compile if Object is two dimensional array.

package Package1;
import org.testng.annotations.Test;
public class Test1
{

@Test
public void NewTest()
{
    Object[][] retval = new Object[3][];

    int i = 0;
    String methodName = "NewTest";
    String className = this.getClass().toString();
    String desc = "This is a test";

    TestTest tt = new TestTest(methodName, className, desc); 
    System.out.println(tt.str1);
    System.out.println(tt.str2);
    System.out.println(tt.str3);

    (new Object[1])[0] =    tt; 
        retval[0] = new Object[1];    
        retval[1] = new Object[1];
        retval[2] = new Object[1];
        System.out.println("object 0 = " + retval[0]);
        System.out.println("object 1 = " + retval[1]);
        System.out.println("object 2 = " + retval[2]);
}

}

package Package1;

public class TestTest 
{

String str1 = "apple";
String str2 = "grape";
String str3 = "orange";


public TestTest(String a, String b, String c)
{
    this.str1 = a;
    this.str2 = b;
    this.str3 = c;
}

}

回答1:

Remember that creating a 2D array is just making an array of arrays. The length of the arrays within the 2D array is no concern of the array holding them.
```
 Object[][] r = new Object[3][];
 Object[] j = new Object[2];

 r[0] = j;
```

In this example, we create a 2D array 'r' that can hold 3 arrays. Then we define a 1D array 'j' that can hold 2 Objects. Then we set the first array of 'r' to be 'j'.

However, if you want the length of the arrays within your 2D array to be a specific value; you will have to assign it a value.

Remember that referring to an index in an array is the same no matter the dimension of the array. What the array contains will be different however.

来源：https://stackoverflow.com/questions/65117157/can-we-define-new-object3-without-defining-number-of-columns

标签

selenium-webdriver

multidimensional-array