被访问者：
<pre>
public abstract class Staff {
//名称
public String name;
//关键绩效指标
public int kpi;

public Staff(String name) {
    this.name = name;
    this.kpi = new Random().nextInt(10);
}

public abstract void accept(Visitor visitor);

}
public class Engineer extends Staff {
private int codeNum;

public Engineer(String name) {
    super(name);
    this.codeNum = new Random().nextInt(10 * 10000);
}

public int getCodeNum() {
    return codeNum;
}

@Override
public void accept(Visitor visitor) {
    visitor.visit(this);
}

}

public class Manager extends Staff {

public int engineerNum;

public Manager(String name) {
    super(name);
    engineerNum = new Random().nextInt(10) * 10;
}

public int getEngineerNum() {
    return engineerNum;
}

@Override
public void accept(Visitor visitor) {
    visitor.visit(this);
}

}
</pre>
访问者：
<pre>
public interface Visitor {
public void visit(Manager manager);

public void visit(Engineer engineer);

}
public class CTO implements Visitor {
private static final String TAG = "CEO";

@Override
public void visit(Manager manager) {
    Log.i(TAG, "经理：" + manager.name + "的手下工程师数：" + manager.getEngineerNum());
}

@Override
public void visit(Engineer engineer) {
    Log.i(TAG, "工程师：" + engineer.name + "的代码数：" + engineer.getCodeNum());
}

}
public class CEO implements Visitor {
private static final String TAG = "CEO";

@Override
public void visit(Manager manager) {
    Log.i(TAG, "经理：" + manager.name + "的绩效：" + manager.kpi);
}

@Override
public void visit(Engineer engineer) {
    Log.i(TAG, "工程师：" + engineer.name + "的绩效：" + engineer.kpi);
}

}
</pre>
使用：
<pre>
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ArrayList<Staff> staffList = new ArrayList<>();
    staffList.add(new Manager("赵经理"));
    staffList.add(new Engineer("工程师-aaaa"));
    staffList.add(new Engineer("工程师-bbbb"));
    staffList.add(new Engineer("工程师-cccc"));
    staffList.add(new Engineer("工程师-dddd"));

    CTO cto = new CTO();
    CEO ceo = new CEO();
    Log.i(TAG, "CTO审阅");
    for (Staff staff : staffList) {
        staff.accept(cto);

    }
    Log.i(TAG, "CEO审阅");
    for (Staff staff : staffList) {
        staff.accept(ceo);
    }
}

}
</pre>
log：
<pre>
03-21 21:05:24.723 32044-32044/com.lerz.visitdemo I/MainActivity: CTO审阅
03-21 21:05:24.723 32044-32044/com.lerz.visitdemo I/CEO: 经理：赵经理的手下工程师数：20
03-21 21:05:24.723 32044-32044/com.lerz.visitdemo I/CEO: 工程师：工程师-aaaa的代码数：42811
03-21 21:05:24.723 32044-32044/com.lerz.visitdemo I/CEO: 工程师：工程师-bbbb的代码数：66016
03-21 21:05:24.724 32044-32044/com.lerz.visitdemo I/CEO: 工程师：工程师-cccc的代码数：89266
03-21 21:05:24.724 32044-32044/com.lerz.visitdemo I/CEO: 工程师：工程师-dddd的代码数：1125
03-21 21:05:24.724 32044-32044/com.lerz.visitdemo I/MainActivity: CEO审阅
03-21 21:05:24.724 32044-32044/com.lerz.visitdemo I/CEO: 经理：赵经理的绩效：5
03-21 21:05:24.724 32044-32044/com.lerz.visitdemo I/CEO: 工程师：工程师-aaaa的绩效：3
03-21 21:05:24.724 32044-32044/com.lerz.visitdemo I/CEO: 工程师：工程师-bbbb的绩效：8
03-21 21:05:24.724 32044-32044/com.lerz.visitdemo I/CEO: 工程师：工程师-cccc的绩效：8
03-21 21:05:24.724 32044-32044/com.lerz.visitdemo I/CEO: 工程师：工程师-dddd的绩效：3
</pre>