Trying to save values to class Object

Question

I posted a question in the past but didn't get any response so I'm assuming my question wasn't clear. Can we define new Object[3][] without defining number of columns? Hoping following code is more readable and easy to understand.

Question: Why is retval[0] always null?

Please help. Thanks,

package YTesting1.YTesting1;

import org.testng.annotations.Test;

public class Test1 {
    
    @Test
    public void MyTest() {
          Object[][] retval = new Object[1][];      
          String mm = "Hello";
          String o = "World";
          String s = "Yeaah";
        
          (new Object[1])[0] = new Test2(mm, o, s); 
           retval[0] = new Object[1];
           
           System.out.println("retval = " +retval[0]);
    }
}

package YTesting1.YTesting1;

public class Test2 {
     private String str1 = "";    
     private String str2 = "";    
     private String str3= "";
  
    public Test2(String lstr1, String lstr2, String lstr3){
            this.str1 = lstr1;
            this.str2 = lstr2;
            this.str3 = lstr3;
    }
}

Answer 1

retval[0] is not null, it is assigned to an empty array of Object.

It is possible to assign to retval[0] some another array and populate it without indicating the number of columns

public static void main(String ... args) {
    Object[][] retval = new Object[1][];      
    String mm = "Hello";
    String o = "World";
    String s = "Yeaah";
        
    //(new Object[1])[0] = new Test2(mm, o, s); 
    retval[0] = new Object[1];
           
    System.out.println("retval[0] = " + retval[0]);
    System.out.println("retval[0][0] = " +retval[0][0]);
    System.out.println("retval = " + Arrays.deepToString(retval));

    retval[0] = new String[] { // 3-element string array
      mm, o, s  
    };
    System.out.println("retval[0] = " + retval[0]);
    System.out.println("retval[0][0] = " +retval[0][0]);
    System.out.println("retval = " + Arrays.deepToString(retval));
}

Output:

retval[0] = [Ljava.lang.Object;@5479e3f
retval[0][0] = null
retval = [[null]]
retval[0] = [Ljava.lang.String;@66133adc
retval[0][0] = Hello
retval = [[Hello, World, Yeaah]]