parameter x of type array

[Ricardo De Jesus]

Hello,

Anybody can help me please? I am trying to understand the line 5, What is the meaning of having only x instead of numbers to define the vector v2?. Below is the code:

public class VarArgs {
	public static void main (String[] args) {
	double[] x = { 9, 8, 7, 4};
	Vector v1 = new Vector(4, 5, 6);
	Vector v2 = new Vector(x);
	Vector v3 = new Vector(1, 1, 1, 1, 1);
	v1.print("v1");
	v2.print("v2");
	v3.print("v3");
	}
}

When I run the programm I get:

v1 = ( 4.00000e+00, 5.00000e+00, 6.00000e+00)^T
v2 = ( 9.00000e+00, 8.00000e+00, 7.00000e+00, 4.00000e+00)^T
v3 = ( 1.00000e+00, 1.00000e+00, 1.00000e+00, 1.00000e+00, 1.00000e+00)^T

Was it the vector v2 generated randomly?

[Jeff Verdegan]

Hi, and welcome to the Ranch!

In the future, when posting code, please UseCodeTags(←click). This will make your code more readable, and will automatically add line numbers.

As for your question, there's nothing random about it. You're passing a reference to an array of doubles to the constructor--the exact doubles that you're seeing printed out for v2. Presumably that Vector constructor iterates through the array, adding each element to itself. This is exactly the behavior I'd expect.

[Ricardo De Jesus]

Thank you for the explanation.
Yes, I just saw the numbers of the vector to be printed in the output.

[Campbell Ritchie]

I have added code tags, since you are new, and also had to remove the line numbers. You will see the code tags add their own line numbers.

[Ricardo De Jesus]

Hello Campbell,

Thank you for editing the code. I will take that into account next time I have a question to post.

Best regards.

Ricardo.

[Campbell Ritchie]

Why are you using Vector? Have you got an old book? Vector has been legacy code for about 12 years.
Why are you not parametrising the Vector? I think you must tell us where the question is from before we can understand it fully. That is because some books introduce confusing elements into questions. You would do well to read the documentation for Vector, which may help you understand what is happening.

[Campbell Ritchie]

I cannot find a print() method in the Vector class I quoted earlier. Where does this Vector class come from? You would need to inspect it before you can understand that code.

[Campbell Ritchie]

Please continue all discussion here.