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建造者模式（Builder）

backend 2025/7/13 6:27:26

Builder模式概述

Builder模式是一种创建型设计模式，通过分步骤构建复杂对象而非一次性创建。它特别适用于需要创建包含多个可选参数的对象场景。

核心思想

将复杂对象的构建与表示分离
提供流畅的API接口
支持链式调用
确保对象创建的一致性和完整性

典型结构

1. 产品类(Product)

public class Computer {private String cpu;private String memory;private String storage;private String graphicsCard;// 构造函数、getter和setter方法
}

2. 抽象建造者(Builder)

public abstract class ComputerBuilder {protected Computer computer = new Computer();public abstract void buildCpu();public abstract void buildMemory();public abstract void buildStorage();public abstract void buildGraphicsCard();public Computer getResult() {return computer;}
}

3. 具体建造者(ConcreteBuilder)

public class GamingComputerBuilder extends ComputerBuilder {@Overridepublic void buildCpu() {computer.setCpu("Intel i9-12900K");}@Overridepublic void buildMemory() {computer.setMemory("32GB DDR5");}@Overridepublic void buildStorage() {computer.setStorage("2TB NVMe SSD");}@Overridepublic void buildGraphicsCard() {computer.setGraphicsCard("RTX 4090");}
}

4. 指挥者(Director)

public class ComputerDirector {private ComputerBuilder builder;public void setBuilder(ComputerBuilder builder) {this.builder = builder;}public Computer construct() {builder.buildCpu();builder.buildMemory();builder.buildStorage();builder.buildGraphicsCard();return builder.getResult();}
}

实现方式(链式调用)

现代Java中更常用的链式调用方式：

public class Computer {private String cpu;private String memory;private String storage;private String graphicsCard;private Computer() {} // 私有构造函数public static class Builder {private Computer computer = new Computer();public Builder cpu(String cpu) {computer.cpu = cpu;return this;}public Builder memory(String memory) {computer.memory = memory;return this;}public Builder storage(String storage) {computer.storage = storage;return this;}public Builder graphicsCard(String graphicsCard) {computer.graphicsCard = graphicsCard;return this;}public Computer build() {// 验证逻辑if (computer.cpu == null) {throw new IllegalStateException("CPU is required");}return computer;}}// getter方法public String getCpu() { return cpu; }public String getMemory() { return memory; }public String getStorage() { return storage; }public String getGraphicsCard() { return graphicsCard; }
}

使用示例

// 游戏电脑配置
Computer gamingComputer = new Computer.Builder().cpu("Intel i9-12900K").memory("32GB DDR5").storage("2TB NVMe SSD").graphicsCard("RTX 4090").build();// 办公电脑配置
Computer officeComputer = new Computer.Builder().cpu("Intel i5-12400").memory("16GB DDR4").storage("512GB SSD").build();