建造者模式的扩展

模式扩展

建造者模式除了上面的用途外，在开发中还有一个常用的使用方式，

就是当一个类构造器需要传入很多参数时，如果创建这个类的实例，代码可读性会非常差，而且很容易引入错误，

此时就可以利用建造者模式进行重构。

重构前代码如下：

public class Phone {
    private String cpu;
    private String screen;
    private String memory;
    private String mainboard;
​
    public Phone(String cpu, String screen, String memory, String mainboard) {
        this.cpu = cpu;
        this.screen = screen;
        this.memory = memory;
        this.mainboard = mainboard;
    }
​
    public String getCpu() {
        return cpu;
    }
​
    public void setCpu(String cpu) {
        this.cpu = cpu;
    }
​
    public String getScreen() {
        return screen;
    }
​
    public void setScreen(String screen) {
        this.screen = screen;
    }
​
    public String getMemory() {
        return memory;
    }
​
    public void setMemory(String memory) {
        this.memory = memory;
    }
​
    public String getMainboard() {
        return mainboard;
    }
​
    public void setMainboard(String mainboard) {
        this.mainboard = mainboard;
    }
​
    @Override
    public String toString() {
        return "Phone{" +
                "cpu='" + cpu + '\'' +
                ", screen='" + screen + '\'' +
                ", memory='" + memory + '\'' +
                ", mainboard='" + mainboard + '\'' +
                '}';
    }
}

public class Client {
    public static void main(String[] args) {
        //构建Phone对象
        Phone phone = new Phone("intel","三星屏幕","金士顿","华硕");
        System.out.println(phone);
    }
}

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上面在客户端代码中构建Phone对象，传递了四个参数，如果参数更多呢？

代码的可读性及使用的成本就是比较高。

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重构后代码：

Phone.java

package com.itheima.pattern.builder.demo2;


/**
 * @version v1.0
 * @ClassName: Phone
 * @Description: 手机类
 * @Author: dym
 */
public class Phone {

    private String cpu;
    private String screen;
    private String memory;
    private String mainboard;

    //私有构造方法
    private Phone(Builder builder) {
        this.cpu = builder.cpu;
        this.screen = builder.screen;
        this.memory = builder.memory;
        this.mainboard = builder.mainboard;
    }

    @Override
    public String toString() {
        return "Phone{" +
                "cpu='" + cpu + '\'' +
                ", screen='" + screen + '\'' +
                ", memory='" + memory + '\'' +
                ", mainboard='" + mainboard + '\'' +
                '}';
    }

    public static final class Builder {
        private String cpu;
        private String screen;
        private String memory;
        private String mainboard;

        public Builder cpu(String cpu) {
            this.cpu = cpu;
            return this;
        }

        public Builder screen(String screen) {
            this.screen = screen;
            return this;
        }
        public Builder memory(String memory) {
            this.memory = memory;
            return this;
        }
        public Builder mainboard(String mainboard) {
            this.mainboard = mainboard;
            return this;
        }

        //使用构建者创建Phone对象
        public Phone build() {
            return new Phone(this);
        }
    }
}

Client.java

package com.itheima.pattern.builder.demo2;

/**
 * @version v1.0
 * @ClassName: Client
 * @Description: TODO(一句话描述该类的功能)
 * @Author: dym
 */
public class Client {
    public static void main(String[] args) {
        //创建手机对象   通过构建者对象获取手机对象
        Phone phone = new Phone.Builder()
                .cpu("intel")
                .screen("三星屏幕")
                .memory("金士顿内存条")
                .mainboard("华硕主板")
                .build();

        System.out.println(phone);
    }
}

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重构后的代码在使用起来更方便，某种程度上也可以提高开发效率。