在Java的一行中声明多个对象

Question

I'm coding in java and I have a class Point with 3 differents constructors. I would like to create 3 objects with each constructor is one line. This is what I wrote :

Point p1 = new Point();
Point p2 = new Point(0.5, 6.);
Point p3 = new Point(p2);

Is it possible to write this on a single line ? Thanks !

Answer 1

You mean :

Point p1 = new Point(), p2 = new Point(0.5, 6.), p3 = new Point(p2);

I assume you have three different constructor in Point class.

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But note, be careful, it will not work if you do :

Point p1 = new Point(), p3 = new Point(p2), p2 = new Point(0.5, 6.);// Error
                                       ^^   ^^ 

In this case the order is important, you have to evaluate the first Object p1 then you can create the 3rd Object p3 based on the 2nd one.

Answer 2

Simple answer: not really.

Of course, you can just avoid the line break, and put

Point p1 = ... ; Point p2 = ...

on one line. Or:

Point p1 = new Point(), p2 = new Point(0.5, 6.), p3 = new Point(p2);

turning ;+linebreak into commas.

And just for the record: alone the fact that you are naming things "point1, point2, point3" is indicating that you are probably doing something wrong. Putting an index into the variable name basically means that you should rather use an array, list, or map.

The other important thing: your intention is always always always to write code that is easy to read and understand for other humans. Stuffing more information into a single line is (very often) not helping with this goal.

Answer 3

当然。

Point p1 = new Point(), p2 = new Point(0.5, 6), p3 = new Point(p2);

Answer 4

You can write each statements in a single line seperated by semi colon .

Point p1 = new Point(); Point p2 = new Point(0.5, 6.); Point p3 = new Point(p2);

or

Point p1 = new Point(), p2 = new Point(0.5, 6.), p3 = new Point(p2);

So line breaks can be avoided in java.

If you use scala , then concept of case classes can be used to achieve your expectation . In scala we don't need to use new keyword to instantiate an object . You can create the instannce directly as

val p1 = Point() or val p2 = Point(0.5,6.) or val p3 = Point(p2) .

But you should have a suitable case class Point for this .