判断两个矩形是否相交，相交区域面积

package companyChuKongKeJi;

// 两个矩形都是平行于X,Y轴，判断是否相交。两种方法，都需要检查特殊情况。
public class RectangleIntersect {
// 方法一：矩阵在X,Y轴上的投影都在另一矩形投影的一侧，则矩阵必定无交集；否则，有交集。
boolean isRectIntersect(Rectangle a, Rectangle b) {
// 需要排除特殊情况：一个矩形在另一个矩形内
if ((a.top < b.top && a.bottom > b.bottom && a.right < b.right && a.left > b.left) || (b.top < a.top && b.bottom > a.bottom && b.right < a.right && b.left > a.left)) {
return false;
}
if ((a.top < b.bottom && a.right < b.left) || (a.bottom > b.top && a.left > b.right)) {
return false;
}
return true;
}

// 方法二：若两矩形的中心满足一定的条件，则必定相交
boolean isRectIntersect2(Rectangle a, Rectangle b) {
float aCenterX = (a.left + a.right) / 2;
float aCenterY = (a.bottom + a.top) / 2;
float bCenterX = (b.left + b.right) / 2;
float bCenterY = (b.bottom + b.top) / 2;
float radiusX = (a.right - a.left) / 2 + (b.right - b.left) / 2;
float radiusY = (a.top - a.bottom) / 2 + (b.top - b.bottom) / 2;
// 需要排除特殊情况：一个矩形在另一个矩形内
if ((a.top < b.top && a.bottom > b.bottom && a.right < b.right && a.left > b.left) || (b.top < a.top && b.bottom > a.bottom && b.right < a.right && b.left > a.left)) {
return false;
}
if ((Math.abs(aCenterX - bCenterX) < radiusX) || (Math.abs(aCenterY - bCenterY) < radiusY)) {
return true;
}
return false;
}

// 若两矩形相交，相交区域必定有：top = min(top),bottom = max(bottom),right =
// min(right),left = max(left)
float intersectArea(Rectangle a, Rectangle b) {
if (isRectIntersect(a, b)) {
return (Math.min(a.top, b.top) - Math.max(a.bottom, b.bottom)) * (Math.min(a.right, b.right) - Math.max(a.left, b.left));
}
return 0;
}

public static void main(String[] args) {
Rectangle ra = new Rectangle(0, 3, 0, 6);
Rectangle rb = new Rectangle(2, 4, 2, 4);
RectangleIntersect r = new RectangleIntersect();
if (r.isRectIntersect(ra, rb)) {
System.out.println("两矩阵相交");
} else {
System.out.println("两矩形不相交");
}
if (r.isRectIntersect2(ra, rb)) {
System.out.println("两矩阵相交");
} else {
System.out.println("两矩形不相交");
}

System.out.println("相交区域面积： " + r.intersectArea(ra, rb));
}
}

class Rectangle {
// 分别表示最上下左右上的坐标
float left;
float right;
float bottom;
float top;

Rectangle(float left, float right, float bottom, float top) {
if (left >= right || top <= bottom) {
System.out.println("矩形坐标初始化错误！");
return;
}
this.left = left;
this.right = right;
this.top = top;
this.bottom = bottom;
}
}