在Java中如何使用多态优化流程代码_行为分发方式的改善

if (obj instanceof Circle) {
    drawCircle((Circle) obj);
} else if (obj instanceof Rectangle) {
    drawRectangle((Rectangle) obj);
} else if (obj instanceof Triangle) {
    drawTriangle((Triangle) obj);
}

interface Shape {
    void draw();
}

class Circle implements Shape {
    public void draw() {
        System.out.println("绘制圆形");
    }
}

class Rectangle implements Shape {
    public void draw() {
        System.out.println("绘制矩形");
    }
}

Shape shape = getShape(); // 返回任意实现
shape.draw(); // 自动执行对应逻辑

interface PaymentStrategy {
    void pay(double amount);
}

class Alipay implements PaymentStrategy {
    public void pay(double amount) {
        System.out.println("使用支付宝支付：" + amount);
    }
}

class WeChatPay implements PaymentStrategy {
    public void pay(double amount) {
        System.out.println("使用微信支付：" + amount);
    }
}

class PaymentContext {
    private PaymentStrategy strategy;

    public void setStrategy(PaymentStrategy strategy) {
        this.strategy = strategy;
    }

    public void executePayment(double amount) {
        strategy.pay(amount);
    }
}

PaymentContext context = new PaymentContext();
context.setStrategy(new Alipay());
context.executePayment(100);

class PaymentFactory {
    public static PaymentStrategy getStrategy(String type) {
        return switch (type) {
            case "alipay" -> new Alipay();
            case "wechat" -> new WeChatPay();
            default -> throw new IllegalArgumentException("不支持的支付方式");
        };
    }
}

PaymentStrategy strategy = PaymentFactory.getStrategy("alipay");
context.setStrategy(strategy);
context.executePayment(200);