构造器模式_组装复杂实例（逐步构造出一个复杂的实例）

/** * 指挥者 * @author maikec * @date 2019/5/11 */public class Director {    private final AbstractBuilder builder;    public Director(AbstractBuilder builder){        this.builder = builder;    }    public void builderMessage(){        builder.createHead();        builder.createBody();        builder.signature();    }}/** * 抽象构造器 * @author maikec * @date 2019/5/11 */public abstract class AbstractBuilder {    protected Message message;    protected Head head;    protected Body body;    protected Author author;    /**     * 创建消息头部     * @return     */    protected abstract Head createHead();    /**     * 创建消息体     * @return     */    protected abstract Body createBody();    /**     * 署名     * @return     */    protected abstract Author signature();    public Message getMessage(){        return message;    }}/** * @author maikec * @date 2019/5/11 */public class Message {    private Head head;    private Body body;    private Author author;    public Message(){}    public Message(Head head,Body body,Author author){        this.head = head;        this.body = body;        this.author = author;    }    @Override    public String toString() {         super.toString();         if (head !=null || body != null || author != null){             StringBuffer sb = new StringBuffer( "[" );             if (head != null){                 sb.append( head.toString() );             }             if (body != null){                 sb.append( body.toString() );             }             if (author != null){                 sb.append( author.toString() );             }             sb.append( "]" );             return sb.toString();         }         return null;    }}/** * @author maikec * @date 2019/5/11 */public class Head {    private String name;    public Head(){}    public Head(String name){        this.name = name;    }    @Override    public String toString() {        super.toString();        return name == null ? "Head" : name;    }}/** * @author maikec * @date 2019/5/11 */public class Body {    private String name;    public Body(){}    public Body(String name) {        this.name = name;    }    @Override    public String toString() {         super.toString();         return name == null ? "Body" : name;    }}/** * @author maikec * @date 2019/5/11 */public class Author {    private String name;    public Author(){}    public Author(String name) {        this.name = name;    }    @Override    public String toString() {         super.toString();         return name == null ? "Author" : name;    }}/** * Email构造器 * @author maikec * @date 2019/5/11 */public class EmailBuilder extends AbstractBuilder {    @Override    protected Head createHead() {         head = new Head("Email Head");         return head;    }    @Override    protected Body createBody() {        body = new Body("Email Body");        return body;    }    @Override    protected Author signature() {        author =  new Author("maikec");        return author;    }    @Override    public Message getMessage() {        return new Message( head,body,author );    }}复制代码

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