设计模式系统回顾（10）建造者模式

原创已于 2022-02-10 16:36:54 修改 · 113 阅读

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#java #设计模式

于 2022-02-10 16:33:59 首次发布

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本文通过一个具体的 Homework 类，展示了如何运用建造者模式来分离对象构建和表示，使得在不改变构建过程的情况下，可以创建不同表示的 Homework 实例。在 TestBuilder 类中，我们创建并配置了一个 Homework 对象，强调了建造者模式的灵活性和封装性。同时，文章也指出了建造者模式相对于工厂模式的优点和缺点。

将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的表示

public class Homework {
    private String easyQc;//简答题目

    private String normalQc;//正常题目

    private String MediumQc;//中等难度题目

    private String HardQc;//困难题目

    public String getEasyQc() {
        return easyQc;
    }

    public void setEasyQc(String easyQc) {
        this.easyQc = easyQc;
    }

    public String getNormalQc() {
        return normalQc;
    }

    public void setNormalQc(String normalQc) {
        this.normalQc = normalQc;
    }

    public String getMediumQc() {
        return MediumQc;
    }

    public void setMediumQc(String mediumQc) {
        MediumQc = mediumQc;
    }

    public String getHardQc() {
        return HardQc;
    }

    public void setHardQc(String hardQc) {
        HardQc = hardQc;
    }
}


public abstract class HomeworkBuilder {
    public abstract HomeworkBuilder buildEasyQc(String easyQc);

    public abstract HomeworkBuilder buildNormalQc(String normalQc);

    public abstract HomeworkBuilder buildMediumQc(String mediumQc);

    public abstract HomeworkBuilder buildHardQc(String hardQc);

    public abstract Homework build();
}


public class ConcreateBuilder extends HomeworkBuilder {
    private Homework homework;

    public ConcreateBuilder(Homework homework) {
        this.homework = homework;
    }

   @Override
    public HomeworkBuilder buildEasyQc(String easyQc) {
        homework.setEasyQc(easyQc);
        return this;
    }

    @Override
    public HomeworkBuilder buildNormalQc(String normalQc) {
        homework.setNormalQc(normalQc);
        return this;
    }

    @Override
    public HomeworkBuilder buildMediumQc(String mediumQc) {
        homework.setMediumQc(mediumQc);
        return this;
    }

    @Override
    public HomeworkBuilder buildHardQc(String hardQc) {
        homework.setHardQc(hardQc);
        return this;
    }

    @Override
    public Homework build() {
        return homework;
    }
}

public class TestBuilder {
    public static void main(String[] args) {
        Homework homework = new Homework();
        HomeworkBuilder homeworkBuilder = new ConcreateBuilder(homework);
        homeworkBuilder.buildEasyQc("我是一道简单题目")
                .buildNormalQc("我是一道标准难度题目")
                .buildMediumQc("我是一道中等难度题目")
                .buildHardQc("我是一道高难度题目");
        homework = homeworkBuilder.build();

        StringBuilder sb = new StringBuilder();
        sb.append(null == homework.getEasyQc() ? "" : homework.getEasyQc() + ",");
        sb.append(null == homework.getNormalQc() ? "" : homework.getNormalQc() + ",");
        sb.append(null == homework.getMediumQc() ? "" : homework.getMediumQc() + ",");
        sb.append(null == homework.getHardQc() ? "" : homework.getHardQc());

        System.out.println("我的家庭作业有：" + sb.toString());
    }
}

建造者和工厂模式的区别在于建造者更加灵活，支持自己搭配
优点
封装和拓展性好
缺点
产品变化时修改成本较大