继承

继承的作用：代码的复用

1)通过extends关键字实现

2)子类可以从父类继承所有非pravite的属性和方法作为自己的成员

5、建立三个类：居民、成人、官员。居民包含身份证号、姓名、出生日期，而成人继承自居民，多包含学历、职业两项数据；官员则继承自成人，多包含党派、职务两项数据。 要求每个类的字段都以属性的方式对外提供数据输入输出的功能。

class resident
{
    int identificationID;
    String Name;
    String Birthday;
    public resident(int a,String b, String c)
     {
         identificationID=a;
         Name=b;
         Birthday=c;
       }
    public void output1()
     {
         System.out.println("identificationID="+identificationID+"Name="+Name+"Birthday="+Birthday);
      }
   }
class adult extends resident
   {
      String Education;
      String Occupation;
      public adult ( int identificationID, String Name,String Birthday,String Education,String Occupation)
        {
            super(identificationID,Name,Birthday);
            this.Education=Education;
            this.Occupation=Occupation;
         }
      public void output2()
      {
           System.out.println("identificationID="+identificationID+"Name="+Name+"Birthday="+Birthday+"Education="

           +Education+"Occupation="+Occupation);
       }
  }
class officer extends adult
  {
      String Party;
      String Post;
      public officer ( int identificationID, String Name,String Birthday,String Education,String Occupation,String Party,String Post)
      {
          super(identificationID,Name,Birthday,Education,Occupation);
          this.Party=Party;
          this.Post=Post;
       }
       public void output3()
       {
           System.out.println("identificationID="+identificationID+"Name="+Name+"Birthday="+Birthday+"Education="+Education+"Occupation="

            +Occupation+"Party="+Party+"Post="+Post);
        }
  }

public class Test
{
     public static void main(String[] args)
     {
         resident man1=new resident(1234567890,"张飞","1932-12-11");
         adult man2=new adult(7654321,"里斯","1273-12-13","大学","会计");
         officer man3=new officer(1568908,"王二小","1993-2-25","小学","游民","民主党","排长");
         man1.output1();
         man2.output2();
         man3.output3();
       }
 }

 运行效果：