建造者模式：是由多个简单的对象一步一步构造成一个复杂的对象。这种模式就是建造者，提供了构造复杂对象的实现方式。

建造者由一下几大部分组成：

1.Product： 创建的复杂对象
2.Builder: 给出一个抽象接口，表示出这个复杂对象由那些组件组成。这个接口只给出由那些组件组成，并不对他们做出实现。
3.ConcreteBuilder： 实现Builder，对复杂对象的各个组件做出具体实现。在建造完成后给出具体的复杂对象。
4.Director：通过ConcreteBuilder获取复杂对象的各个组件来得到复杂对象。不需要参与各个组件的实现，只负责保证复杂对象的各组件完成创建或者按组件某种顺序创建。

建造者

比如创建一个复杂红包的示例：
Product：

public class RedPacket {
    
    private String publisherName; //发包人

    private String acceptName; //收包人

    private BigDecimal packetAmount; //红包金额

    private int packetType; //红包类型

    private Date pulishPacketTime; //发包时间

    private Date openPacketTime; //抢包时间

    public RedPacket(String publisherName, String acceptName, BigDecimal packetAmount, int packetType, Date pulishPacketTime, Date openPacketTime) {
        this.publisherName = publisherName;
        this.acceptName = acceptName;
        this.packetAmount = packetAmount;
        this.packetType = packetType;
        this.pulishPacketTime = pulishPacketTime;
        this.openPacketTime = openPacketTime;
    }

    public String getPublisherName() {
        return publisherName;
    }

    public void setPublisherName(String publisherName) {
        this.publisherName = publisherName;
    }

    public String getAcceptName() {
        return acceptName;
    }

    public void setAcceptName(String acceptName) {
        this.acceptName = acceptName;
    }

    public BigDecimal getPacketAmount() {
        return packetAmount;
    }

    public void setPacketAmount(BigDecimal packetAmount) {
        this.packetAmount = packetAmount;
    }

    public int getPacketType() {
        return packetType;
    }

    public void setPacketType(int packetType) {
        this.packetType = packetType;
    }

    public Date getPulishPacketTime() {
        return pulishPacketTime;
    }

    public void setPulishPacketTime(Date pulishPacketTime) {
        this.pulishPacketTime = pulishPacketTime;
    }

    public Date getOpenPacketTime() {
        return openPacketTime;
    }

    public void setOpenPacketTime(Date openPacketTime) {
        this.openPacketTime = openPacketTime;
    }

    @Override
    public String toString() {
        return "RedPacket [publisherName=" + publisherName + ", acceptName="
                + acceptName + ", packetAmount=" + packetAmount
                + ", packetType=" + packetType + ", pulishPacketTime="
                + pulishPacketTime + ", openPacketTime=" + openPacketTime + "]";
    }

Builder:

public interface RedPacketBuilder {
    
    RedPacketBuilder setPublisherName(String publishName);

    RedPacketBuilder setAcceptName(String acceptName);

    RedPacketBuilder setPacketAmount(BigDecimal packetAmount);

    RedPacketBuilder setPacketType(int packetType);

    RedPacketBuilder setPulishPacketTime(Date pushlishPacketTime);

    RedPacketBuilder setOpenPacketTime(Date openPacketTime);

    RedPacket build();
}

ConcreteBuilder:

public class RedPacketBuilderImpl implements RedPacketBuilder {
    
    private String publisherName;

    private String acceptName;

    private BigDecimal packetAmount;
    
    private int packetType;

    private Date pulishPacketTime;

    private Date openPacketTime;

    public static RedPacketBuilderImpl getBulider(){
        return new RedPacketBuilderImpl();
    }


    @Override
    public RedPacketBuilder setPublisherName(String publishName) {
        this.publisherName = publishName;
        return this;
    }

    @Override
    public RedPacketBuilder setAcceptName(String acceptName) {
       this.acceptName = acceptName;
       return this;
    }

    @Override
    public RedPacketBuilder setPacketAmount(BigDecimal packetAmount) {
       this.packetAmount = packetAmount;
       return this;
    }

    @Override
    public RedPacketBuilder setPacketType(int packetType) {
        this.packetType = packetType;
        return this;
    }

    @Override
    public RedPacketBuilder setPulishPacketTime(Date pushlishPacketTime) {
       this.pulishPacketTime = pushlishPacketTime;
        return this;
    }

    @Override
    public RedPacketBuilder setOpenPacketTime(Date openPacketTime) {
      this.openPacketTime = openPacketTime;
        return this;
    }


    public RedPacket build() {
        return new RedPacket(publisherName,acceptName,packetAmount,packetType,pulishPacketTime,openPacketTime);
    }

Director:

public class Director {
    
    public static void main(String[] args) {
        RedPacket redPacket = RedPacketBuilderImpl.getBulider().setPublisherName("xxx")
                                                               .setAcceptName("xxx")
                                                               .setPacketAmount(new BigDecimal("888"))
                                                               .setPacketType(1)
                                                               .setOpenPacketTime(new Date())
                                                               .setPulishPacketTime(new Date()).build();

        System.out.println(redPacket);
    }

这样对完成对复杂红包的创建了

运行结果

RedPacket [publisherName=XXX, acceptName=XXX, packetAmount=888, packetType=1, pulishPacketTime=Sun Jun 14 23:03:06 CST 2020, openPacketTime=Sun Jun 14 23:03:06 CST 2020]