1.3: Objects as Parameters

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You can pass objects as parameters in the usual way. For example:

public static void printPoint(Point p) {
    System.out.println("(" + p.x + ", " + p.y + ")");
}

This method takes a point as an argument and displays its attributes in parentheses. If you invoke printPoint(blank), it displays (3, 4).

But we don’t really need a method like printPoint, because if you invoke System.out.println(blank) you get:

java.awt.Point[x=3,y=4]

Point objects provide a method called toString that returns a string representation of a point. When you call println with objects, it automatically calls toString and displays the result. In this case, it shows the name of the type (java.awt.Point) and the names and values of the attributes.

As another example, we can rewrite the distance method from Section 6.2 so that it takes two Points as parameters instead of four doubles.

public static double distance(Point p1, Point p2) {
    int dx = p2.x - p1.x;
    int dy = p2.y - p1.y;
    return Math.sqrt(dx * dx + dy * dy);
}

Passing objects as parameters makes the source code more readable and less error-prone, because related values are bundled together.