/** "Implementor" */
interface DrawingAPI {
public void drawCircle(double x, double y, double radius);
}
/** "ConcreteImplementor" 1/2 */
class DrawingAPI1 implements DrawingAPI {
public void drawCircle(double x, double y, double radius) {
System.out.printf("API1.circle at %f:%f radius %f\n", x, y, radius);
}
}
/** "ConcreteImplementor" 2/2 */
class DrawingAPI2 implements DrawingAPI {
public void drawCircle(double x, double y, double radius) {
System.out.printf("API2.circle at %f:%f radius %f\n", x, y, radius);
}
}
/** "Abstraction" */
interface Shape {
public void draw(); // low-level
public void resizeByPercentage(double pct); // high-level
}
/** "Refined Abstraction" */
class CircleShape implements Shape {
private double x, y, radius;
private DrawingAPI drawingAPI;
public CircleShape(double x, double y, double radius, DrawingAPI drawingAPI) {
this.x = x; this.y = y; this.radius = radius;
this.drawingAPI = drawingAPI;
}
// low-level i.e. Implementation specific
public void draw() {
drawingAPI.drawCircle(x, y, radius);
}
// high-level i.e. Abstraction specific
public void resizeByPercentage(double pct) {
radius *= pct;
}
}
/** "Client" */
class BridgePattern {
public static void main(String[] args) {
Shape[] shapes = new Shape[2];
shapes[0] = new CircleShape(1, 2, 3, new DrawingAPI1());
shapes[1] = new CircleShape(5, 7, 11, new DrawingAPI2());
for (Shape shape : shapes) {
shape.resizeByPercentage(2.5);
shape.draw();
}
}
}
Bridge遵循的是接口隔離原則的典型。比如，隨著時代的發展，槍在不停的變化改進。與此同時槍的子彈也在改進，很多子彈賦予了新功能：比如信號彈，救援彈，甚至是炸彈。這樣，槍是抽象的同時，子彈也是抽象的。二者組合起來變換無窮。仔細想一下《java與模式》中橋梁模式的例子--飛機和飛機制造商是不是也是這種靈活變換的組合？