Thanks.! :)

public Matrix(double[][] elements) {   
  System.out.println("Entered the Constructor");
  try{
    print(elements);                      System.out.println("Passed Printing");
    matrix = clone(elements);             System.out.println("Passed Assignment");
  }catch(NullPointerException e){
    System.out.println("Error - Null \n" + "msg - " + e.getMessage() + "\n----------");
    throw new IllegalArgumentException();
  }catch(IndexOutOfBoundsException e){
    System.out.println("Error - Index\n" + "msg - " + e.getMessage() + "\n----------");
    //throw new RuntimeException();               // - Test Failed
    //throw new IndexOutOfBoundsException();      // - Test Failed
    //throw new NullPointerException();           // - Test Failed
    //throw new IllegalArgumentException();       // - should throw IllegalArgumentException if array is null: expected null, but was:<Matrix@2bbf180e>
    //throw new ArrayIndexOutOfBoundsException(); // - Test Failed
    // No Exception Thrown                        // - should throw IllegalArgumentException if array is null: expected null, but was:<Matrix@769e7ee8>
  }
  System.out.println("Reached Exit");
}

This is the Output Log

Entered the Constructor
Error - Null
msg - null
----------

Entered the Constructor
size => rows = 2 cols = 2
1.0 2.0
Error - Null
msg - null
----------

Entered the Constructor
size => rows = 2 cols = 3
1.0 2.0 3.0
1.0 2.0
Passed Printing
Error - Index
msg - Index 2 out of bounds for length 2
----------

Reached Exit

The Error Message :-
should throw IllegalArgumentException if array is null: expected null, but was:Matrix@769e7ee8

Its always the same data. And the message is the above one or Test Failed. I tried different Exceptions but none worked. Also No Exception still doesn't works.
Cannot use other than runtime Exceptions because the methods in the class creates the Matrix object by this constructor and then returns them. Like -> return new Matrix(someData);

IndexOutOfBoundsException occurs due to the short length (2 rather than 3 as row 1) of 2nd row

What to do.?

public Matrix(double[][] elements) {   
  try{
    matrix = clone(elements); 
  }catch(NullPointerException e){
    throw new IllegalArgumentException();
  }
}

yup throwing the exception but it still wont work.
clone(element) a function to copy all the elements to new array and return.

I pass all the tests except one test1Init.

It says:

test1Init

should throw IllegalArgumentException if array is null: expected null, but was:Matrix@14d3bc22


can someone help.?

Thanks! It worked!