优化这段代码，加入多态，线程

好的，以下是优化后的代码，加入了多态和线程：

public abstract class Insurance {
   private String type;
   private String coverage;
   private double premium;
   
   public Insurance(String type, String coverage, double premium) {
      this.type = type;
      this.coverage = coverage;
      this.premium = premium;
   }
   
   public String getType() {
      return type;
   }
   
   public String getCoverage() {
      return coverage;
   }
   
   public double getPremium() {
      return premium;
   }
   
   public void setType(String type) {
      this.type = type;
   }
   
   public void setCoverage(String coverage) {
      this.coverage = coverage;
   }
   
   public void setPremium(double premium) {
      this.premium = premium;
   }
   
   public abstract void display();

   public void calculatePremium() {
      // 计算保费
      System.out.println("Calculating premium...");
   }

   public void issuePolicy() {
      // 发布保单
      System.out.println("Issuing policy...");
   }
}

public class HealthInsurance extends Insurance {
   public HealthInsurance(String type, String coverage, double premium) {
      super(type, coverage, premium);
   }

   @Override
   public void display() {
      System.out.println("Health Insurance:");
      System.out.println("Type: " + getType());
      System.out.println("Coverage: " + getCoverage());
      System.out.println("Premium: $" + getPremium());
   }
}

public class CarInsurance extends Insurance {
   public CarInsurance(String type, String coverage, double premium) {
      super(type, coverage, premium);
   }

   @Override
   public void display() {
      System.out.println("Car Insurance:");
      System.out.println("Type: " + getType());
      System.out.println("Coverage: " + getCoverage());
      System.out.println("Premium: $" + getPremium());
   }
}

public class InsuranceThread implements Runnable {
   private Insurance insurance;

   public InsuranceThread(Insurance insurance) {
      this.insurance = insurance;
   }

   @Override
   public void run() {
      insurance.calculatePremium();
      insurance.issuePolicy();
   }

   public static void main(String[] args) {
      Insurance healthInsurance = new HealthInsurance("Health", "Medical expenses", 1000.00);
      Insurance carInsurance = new CarInsurance("Car", "Accident damages", 500.00);

      Thread healthThread = new Thread(new InsuranceThread(healthInsurance));
      Thread carThread = new Thread(new InsuranceThread(carInsurance));

      healthThread.start();
      carThread.start();
   }
}

在这个优化后的代码中，我们创建了一个抽象的 Insurance 类，它包含了保险类型、保险覆盖范围和保费等属性，以及一个抽象的 display() 方法用于显示保险介绍信息。同时，我们还加入了 calculatePremium() 和 issuePolicy() 方法，并使用多态实现了 HealthInsurance 和 CarInsurance 类，分别代表健康保险和车辆保险。

在 InsuranceThread 类中，我们使用了 Runnable 接口来实现多线程，以计算保费和发布保单。在 main() 方法中，我们创建了两个不同的保险对象，并使用两个线程分别计算保费和发布保单。通过这样的方式，我们可以提高程序的运行效率，同时实现了多态和线程的应用。