/**
 * 員工基類（Element） 
 */
public abstract class Staff {
  //員工姓名
  public String name;
  //員工KPI
  public int kpi;
  public Staff(String name) {
    super();
    this.name = name;
    this.kpi = new Random().nextInt(10);
  }
  //接受Visitor的訪問(wèn)
  public abstract void accept(Visitor visitor);
}

/**
 * 工程師 
 */
public class Engineer extends Staff{
  private int codeLines;//代碼數(shù)量
  public Engineer(String name) {
    super(name);
    codeLines = new Random().nextInt(10 * 10000);
  }
  @Override
  public void accept(Visitor visitor) {
    visitor.visit(this);
  }
  //工程師這一年寫的代碼數(shù)量
  public int getCodeLines(){
    return codeLines;
  }
}

/**
 * 經(jīng)理
 */
public class Manager extends Staff{
  private int products;//產(chǎn)品數(shù)量
  public Manager(String name) {
    super(name);
    products = new Random().nextInt(10);
  }
  @Override
  public void accept(Visitor visitor) {
    visitor.visit(this);
  }
  //一年內(nèi)做的產(chǎn)品數(shù)量
  public int getProducts(){
    return products;
  }
}

public interface Visitor {
  /**
   * 訪問(wèn)工程師類型
   */
  public void visit(Engineer engineer);
  /**
   * 訪問(wèn)經(jīng)理類型
   */
  public void visit(Manager manager);
}

public class CEOVisitor implements Visitor {
  @Override
  public void visit(Engineer engineer) {
    System.out.println("工程師：" + engineer.name + ", KPI:" + engineer.kpi);
  }
  @Override
  public void visit(Manager manager) {
    System.out.println("經(jīng)理：" + manager.name + ", KPI:" + manager.kpi
        + ", 新產(chǎn)品數(shù)量 ：" + manager.getProducts());
  }
}

public class CTOVisitor implements Visitor {
  @Override
  public void visit(Engineer engineer) {
    System.out.println("工程師：" + engineer.name + ", 代碼數(shù)量:" + engineer.getCodeLines());
  }
  @Override
  public void visit(Manager manager) {
    System.out.println("經(jīng)理：" + manager.name +", 產(chǎn)品數(shù)量 ：" + manager.getProducts());
  }
}

//員工業(yè)務(wù)報(bào)表類（ObjectStructure）
public class BusinessReport {
  List<Staff> mStaffs = new LinkedList<Staff>();
  public BusinessReport() {
    mStaffs.add(new Manager("王經(jīng)理"));
    mStaffs.add(new Engineer("工程師-A"));
    mStaffs.add(new Engineer("工程師-B"));
    mStaffs.add(new Manager("李經(jīng)理"));
    mStaffs.add(new Engineer("工程師-C"));
  }
  /**
   * 為訪問(wèn)者展示報(bào)表 
   * @param visitor 如CEO、CTO
   */
  public void showReport(Visitor visitor){
    for(Staff staff : mStaffs){
      staff.accept(visitor);
    }
  }
}

public class Client {
  public static void main(String[] args) {
    //構(gòu)建報(bào)表
    BusinessReport report = new BusinessReport();
    System.out.println("===== 給CEO看報(bào)表 =====");
    //設(shè)置訪問(wèn)者CEO
    report.showReport(new CEOVisitor());
    System.out.println("===== 給CTO看報(bào)表 =====");
    //設(shè)置訪問(wèn)者CTO
    report.showReport(new CTOVisitor());
  }
}

===== 給CEO看報(bào)表 =====
經(jīng)理：王經(jīng)理, KPI:2, 新產(chǎn)品數(shù)量 ：5
工程師：工程師-A, KPI:5
工程師：工程師-B, KPI:7
經(jīng)理：李經(jīng)理, KPI:9, 新產(chǎn)品數(shù)量 ：8
工程師：工程師-C, KPI:1
===== 給CTO看報(bào)表 =====
經(jīng)理：王經(jīng)理, 產(chǎn)品數(shù)量 ：5
工程師：工程師-A, 代碼數(shù)量:26238
工程師：工程師-B, 代碼數(shù)量:8282
經(jīng)理：李經(jīng)理, 產(chǎn)品數(shù)量 ：8
工程師：工程師-C, 代碼數(shù)量:47927

public interface Element extends javax.lang.model.AnnotatedConstruct {
  /**
   * Returns the {@code kind} of this element.
   *
   * @return the kind of this element
   */
  ElementKind getKind();//獲取元素類型
  //代碼省略
  /**
   * Applies a visitor to this element.
   *
   * @param <R> the return type of the visitor's methods
   * @param <P> the type of the additional parameter to the visitor's methods
   * @param v  the visitor operating on this element
   * @param p  additional parameter to the visitor
   * @return a visitor-specified result
   */
  <R, P> R accept(ElementVisitor<R, P> v, P p);//接受訪問(wèn)者的訪問(wèn)
}

public interface ElementVisitor<R, P> {
  /**
   * Visits an element.
   * @param e the element to visit
   * @param p a visitor-specified parameter
   * @return a visitor-specified result
   */
  R visit(Element e, P p);
  /**
   * A convenience method equivalent to {@code v.visit(e, null)}.
   * @param e the element to visit
   * @return a visitor-specified result
   */
  R visit(Element e);
  /**
   * Visits a package element.
   * @param e the element to visit
   * @param p a visitor-specified parameter
   * @return a visitor-specified result
   */
  R visitPackage(PackageElement e, P p);
  /**
   * Visits a type element.
   * @param e the element to visit
   * @param p a visitor-specified parameter
   * @return a visitor-specified result
   */
  R visitType(TypeElement e, P p);
  /**
   * Visits a variable element.
   * @param e the element to visit
   * @param p a visitor-specified parameter
   * @return a visitor-specified result
   */
  R visitVariable(VariableElement e, P p);
  /**
   * Visits an executable element.
   * @param e the element to visit
   * @param p a visitor-specified parameter
   * @return a visitor-specified result
   */
  R visitExecutable(ExecutableElement e, P p);
  /**
   * Visits a type parameter element.
   * @param e the element to visit
   * @param p a visitor-specified parameter
   * @return a visitor-specified result
   */
  R visitTypeParameter(TypeParameterElement e, P p);
  /**
   * Visits an unknown kind of element.
   * This can occur if the language evolves and new kinds
   * of elements are added to the {@code Element} hierarchy.
   *
   * @param e the element to visit
   * @param p a visitor-specified parameter
   * @return a visitor-specified result
   * @throws UnknownElementException
   * a visitor implementation may optionally throw this exception
   */
  R visitUnknown(Element e, P p);
}