Java建造者模式构建复杂对象的最佳实践

Java建造者模式是一种创建型设计模式，通过一步一步的构建复杂对象来实现构建者模式。

下面是Java建造者模式构建复杂对象的完整攻略：

步骤一：创建一个产品类

创建一个产品类，该类由多个属性组成，并提供setter和getter方法。

public class Computer {
   private String cpu;
   private String memory;
   private String disk;
   private String graphicsCard;

   public String getCpu() {
      return cpu;
   }
   public void setCpu(String cpu) {
      this.cpu = cpu;
   }

   public String getMemory() {
      return memory;
   }
   public void setMemory(String memory) {
      this.memory = memory;
   }

   public String getDisk() {
      return disk;
   }
   public void setDisk(String disk) {
      this.disk = disk;
   }

   public String getGraphicsCard() {
      return graphicsCard;
   }
   public void setGraphicsCard(String graphicsCard) {
      this.graphicsCard = graphicsCard;
   }    
}

步骤二：创建一个抽象建造者类

创建一个抽象建造者类，该类定义了一个用于建造产品的接口及其需要的方法。

public abstract class ComputerBuilder {
   public abstract void buildCpu();
   public abstract void buildMemory();
   public abstract void buildDisk();
   public abstract void buildGraphicsCard();
   public abstract Computer getComputer();
}

步骤三：创建具体建造者类

创建一个具体的建造者类，实现抽象建造者接口中的方法。

public class LenovoComputerBuilder extends ComputerBuilder {
   private Computer computer = new Computer();

   public void buildCpu() {
      computer.setCpu("Intel Core i7");
   }

   public void buildMemory() {
      computer.setMemory("16G DDR4");
   }

   public void buildDisk() {
      computer.setDisk("1TB SSD");
   }

   public void buildGraphicsCard() {
      computer.setGraphicsCard("NVIDIA RTX 2060");
   }

   public Computer getComputer() {
      return computer;
   }
}

步骤四：创建一个指导者类

创建一个指导者类，用于使用建造者接口中的方法来建造产品对象。

public class Director {
   private ComputerBuilder computerBuilder;

   public void setComputerBuilder(ComputerBuilder computerBuilder) {
      this.computerBuilder = computerBuilder;
   }

   public void constructComputer() {
      computerBuilder.buildCpu();
      computerBuilder.buildMemory();
      computerBuilder.buildDisk();
      computerBuilder.buildGraphicsCard();
   }
}

步骤五：使用建造者模式构建复杂对象

使用建造者模式构建复杂对象。

public class Client {
   public static void main(String[] args) {
      Director director = new Director();
      ComputerBuilder builder = new LenovoComputerBuilder();
      director.setComputerBuilder(builder);
      director.constructComputer();
      Computer computer = builder.getComputer();
      System.out.println("CPU: " + computer.getCpu());
      System.out.println("Memory: " + computer.getMemory());
      System.out.println("Disk: " + computer.getDisk());
      System.out.println("Graphics card: " + computer.getGraphicsCard());
   }
}

以上就是使用Java建造者模式构建复杂对象的完整攻略。下面是两个示例说明。

示例1

如果我们想要另一台具有不同特征的电脑，我们可以使用另一个具体构建者类。

public class HpComputerBuilder extends ComputerBuilder {
   private Computer computer = new Computer();

   public void buildCpu() {
      computer.setCpu("AMD Ryzen 7");
   }

   public void buildMemory() {
      computer.setMemory("32G DDR4");
   }

   public void buildDisk() {
      computer.setDisk("2TB SSD");
   }

   public void buildGraphicsCard() {
      computer.setGraphicsCard("NVIDIA RTX 3080");
   }

   public Computer getComputer() {
      return computer;
   }
}

在客户端代码处，只需要更改建造者对象为HpComputerBuilder即可。

public class Client {
   public static void main(String[] args) {
      Director director = new Director();
      ComputerBuilder builder = new HpComputerBuilder();
      director.setComputerBuilder(builder);
      director.constructComputer();
      Computer computer = builder.getComputer();
      System.out.println("CPU: " + computer.getCpu());
      System.out.println("Memory: " + computer.getMemory());
      System.out.println("Disk: " + computer.getDisk());
      System.out.println("Graphics card: " + computer.getGraphicsCard());
   }
}

示例2

我们可以调用具体建造者中的任何方法来构建电脑对象的组件。例如，我们可以在不修改Computer类的情况下添加其他组件。

public class LenovoComputerBuilder extends ComputerBuilder {
   private Computer computer = new Computer();

   public void buildCpu() {
      computer.setCpu("Intel Core i7");
   }

   public void buildMemory() {
      computer.setMemory("16G DDR4");
   }

   public void buildDisk() {
      computer.setDisk("1TB SSD");
   }

   public void buildGraphicsCard() {
      computer.setGraphicsCard("NVIDIA RTX 2060");
   }

   public void buildExtraComponent() {
      computer.setExtraComponent("Wireless mouse and keyboard set");
   }

   public Computer getComputer() {
      return computer;
   }
}

在客户端处，我们可以轻松地使用新方法。

public class Client {
   public static void main(String[] args) {
      Director director = new Director();
      ComputerBuilder builder = new LenovoComputerBuilder();
      director.setComputerBuilder(builder);
      director.constructComputer();
      LenovoComputerBuilder lenovoComputerBuilder = (LenovoComputerBuilder) builder;
      lenovoComputerBuilder.buildExtraComponent();
      Computer computer = builder.getComputer();
      System.out.println("CPU: " + computer.getCpu());
      System.out.println("Memory: " + computer.getMemory());
      System.out.println("Disk: " + computer.getDisk());
      System.out.println("Graphics card: " + computer.getGraphicsCard());
      System.out.println("Extra component: " + computer.getExtraComponent());
   }
}

以上就是两个示例说明。