[英]Objects switching between variables in Java
我正在用Java進行一些培訓,但我堅持如何解決這個問題。 如何訪問不同的變量? 例如,我想訪問c1
的x
但它給我0
,這是默認的x
。
這是代碼:
class Circle {
static double x; // x-coordinate of centre
static double y; // y-coordinate of centre
static double r; // radius
static Circle c1;{
c1.x = 1;
c1.y= 2;
c1.r= 4;
double distance = Math.sqrt((x-0)*(x-0) + (y-0)*(y-0));
System.out.println(distance + " " + Math.sqrt((x-0)*(x-0) + (y-0)*(y-0)) );
}
static Circle c2;{
c2.x = -2;
c2.y=0;
c2.r=2;
}
public static void main(String[] args){
double distance = Math.sqrt((c1.x-0)*(c1.x-0) + (c1.y-0)*(c1.y-0));
System.out.println(distance + " " + Math.sqrt((x-0)*(x-0) + (y-0)*(y-0)) );
}
}
您沒有創建任何Circle實例,並且所有變量都是靜態變量,因此x == c1.x == c2.x
(它們都引用完全相同的變量)。
我將擺脫靜態變量並正確初始化實例:
public class Circle
{
double x; // x-coordinate of centre
double y; // y-coordinate of centre
double r; // radius
public static void main(String[] args)
{
Circle c1 = new Circle();
c1.x = 1;
c1.y= 2;
c1.r= 4;
Circle c2 = new Circle ();
c2.x = -2;
c2.y=0;
c2.r=2;
System.out.println("distance " + Math.sqrt((c2.x-c1.x)*(c2.x-c1.x) + (c2.y-c1.y)*(c2.y-c1.y)) );
}
}
您應該學習OOP。 您需要刪除靜態定義並添加實例方法以計算到其他Circle的距離。 這種添加更面向OOP。
這是修改后的代碼:
public class Circle {
private double x;
private double y;
private double r;
public Circle(double x, double y, double r) {
this.x = x;
this.y = y;
this.r = r;
}
public double distanceTo(Circle other) {
double deltaX = other.x - this.x;
double deltaY = other.y - this.y;
return Math.sqrt(deltaX * deltaX + deltaY * deltaY);
}
public double getX() {
return x;
}
public double getY() {
return y;
}
public double getR() {
return r;
}
public static void main(String[] args) {
Circle c1 = new Circle(10, 10, 10);
Circle c2 = new Circle(100, 100, 10);
System.out.println(c1.distanceTo(c2));
}
}
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