Java学习笔记7

 

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java第七天: 接口的作用,接口的思想
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(1) 接口的第一种用途: 实现多继承.(最低的要求.)
例子: 就是让某些子类实现这个接口://在已经形成的树状结构,实现再抽象.
1.在原有的雇员练习上修改代码
公司会给SalaryEmployee每月另外发放2000元加班费,给BasePlusSalesEmployee发放1000元加班费
改写原有代码,加入以上的逻辑
并写一个方法,打印出本月公司总共发放了多少加班费;
package test;

publicclass TestEmployee {

       publicstaticvoid main(String[] args) {

              Employee[] es = new Employee[4];

              es[0] = new SalariedEmployee("Liucy", 10, 8000);

              es[1] = new HourlyEmployee("Chenzq", 2, 20, 300);

              es[2] = new SalesEmployee("DuBin", 8, 100000, 0.05);

              es[3] = new BasePlusSalesEmployee("Hanlj", 10, 30000, 0.2, 5000);

              for (int i = 0; i < es.length; i++) {

                     System.out.print(es[i].getName() + ": ");

                     System.out.println(es[i].getSalary(10));

              }

              double result = 0;

              for (int i = 0; i < es.length; i++) {

                     if (es[i] instanceof addAble) {

                            addAble a = (addAble) es[i];

                            result += a.getAddMoney();

                     }

              }

              System.out.println("总共发的加班费是" + result);

       }

}

class Employee {

       private String name;

       privateintbirthday;

       Employee() {

       }

       Employee(String name, int birthday) {

              this.name = name;

              this.birthday = birthday;

       }

       double getSalary(int month) {

              if (month == birthday) {

                     return 100;

              }

              return 0;

       }

       String getName() {

              returnname;

       }

}

interface addAble {

       double getAddMoney();

}

class SalariedEmployee extends Employee implements addAble {

       privateintmonthsalary;

       SalariedEmployee() {

       }

       SalariedEmployee(String name, int birthday, int monthsalary) {

              super(name, birthday);

              this.monthsalary = monthsalary;

       }

       double getSalary(int month) {

              returnsuper.getSalary(month) + monthsalary + getAddMoney();

       }

       publicdouble getAddMoney() {

              return 2000;

       }

}

class HourlyEmployee extends Employee {

       privateinthoursalary;

       privateinthour;

       HourlyEmployee() {

       }

       HourlyEmployee(String name, int birthday, int hoursalary, int hour) {

              super(name, birthday);

              this.hoursalary = hoursalary;

              this.hour = hour;

       }

       double getSalary(int month) {

              double m = 0;

              if (hour >= 160) {

                     returnsuper.getSalary(month) + hoursalary * 160 + 1.5 * hoursalary

                                   * (hour - 160);

              } else

                     returnsuper.getSalary(month) + hoursalary * hour;

       }

}

class SalesEmployee extends Employee {

       privateintsale;

       privatedoublerate;

       SalesEmployee() {

       }

       SalesEmployee(String name, int birthday, int sale, double rate) {

              super(name, birthday);

              this.sale = sale;

              this.rate = rate;

       }

       double getSalary(int month) {

              returnsuper.getSalary(month) + sale * rate;

       }

}

class BasePlusSalesEmployee extends SalesEmployee implements addAble {

       privateintbasesalary;

       BasePlusSalesEmployee() {

       }

       BasePlusSalesEmployee(String name, int birthday, int sale, double rate,

                     int basesalary) {

              super(name, birthday, sale, rate);

              this.basesalary = basesalary;

       }

       double getSalary(int month) {

              returnsuper.getSalary(month) + basesalary + getAddMoney();

       }

       publicdouble getAddMoney() {

              return 1000;

       }

}
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(2) 接口的单继承:
接口像一个类的额外的信息().
java的多继承是有主次的,有主类型,附加的类型(副类型[接口]是一个附加信息.)
java中的多继承: 区分主类型和次要类型,接口的引用就使得我们可以对事物的共性,作一个再抽象.抽象出副类型.这种多继承的关系,是不会破坏单继承树状关系的复杂度.
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(3) 接口的精华.(没有实现和标准)
最重要的精华,是在于方法没有实现上在于接口是一个标准上,
接口是一种标准.有分工就一定要有接口.接口定义了标准,让分工后的能够  
package test;

publicclass TestJDBC {

       publicstaticvoid main(String[] args) {

              Driver d = getDriver(args[0]); // 这个接口由sun公司制定(多态),把标准的制定者,标准的实现者(二者分离),

              // 标准的使用者.(使用标准.)不同的 [我们是针对接口编程]

              d.connect(); // 传入不同的参数,会调用不同的实现,在这里具体的调用了不同的实现.

       } // 屏蔽接口不同实现的差异.!!!

       publicstatic Driver getDriver(String dbName) {

              if (dbName.equals("MySql"))

                     returnnew MySqlDriver();

              if (dbName.equals("Db2"))

                     returnnew Db2Driver();

              returnnull;

       }

}

// sun公司和数据库厂商,协调出了一个都遵循的标准(接口),接口的定义由sun公司来作,

// 具体的实现由数据库厂商实现

interface Driver { // 这个

       void connect();

}

// MySql

class MySqlDriver implements Driver {

       publicvoid connect() {

              System.out.println("ConnetMySql!!! 呵呵");

       }

}

class Db2Driver implements Driver {

       publicvoid connect() {

              System.out.println("ConnectDb2!! 呵呵");

       }

}

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package test;

publicclass TestJDBC2 {

       publicstaticvoid main(String[] args) { // 这样会造成程序和数据库有强藕合的特性.

              MySqlDriver ss = new MySqlDriver(); // 这些代码都要换,造成重复开发.

              ss.connect();

              Db2Driver dd = new Db2Driver();

              dd.getConnect();

       }

}

class MySqlDriver {

       publicvoid connect() {

              System.out.println("ConnetMySql!!! 呵呵");

       }

}

class Db2Driver {

       publicvoid getConnect() {

              System.out.println("ConnectDb2!! 呵呵");

       }

}
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package test;

publicclass TestArray {

       publicstaticvoid main(String[] args) {

              int i = Integer.parseInt(args[0]);

              ArrayTool at;

              if (i == 0)

                     at = new ArrayTool1();

              else

                     at = new ArrayTool2();

              User u = new User();

              u.method(at);

       }

}

class User {

       publicvoid method(ArrayTool at) {

              int[] a = { 1, 3, 4, 6, 5, 0, 0, 0 };

              int index = 5;

              a = at.insert(a, index, 2, 7);

              for (int i = 0; i < a.length; i++) {

                     System.out.print(a[i] + "/t");

              }

              System.out.println();

       }

}

class ArrayTool1 implements ArrayTool {

       publicint[] insert(int[] data, int index, int pos, int value) {

              for (int i = index; i > pos; i--) {

                     data[i] = data[i - 1];

              }

              data[pos] = value;

              return data;

       }

}

class ArrayTool2 implements ArrayTool {

       publicint[] insert(int[] data, int index, int pos, int value) {

              int[] data2 = newint[data.length + 1];

              System.arraycopy(data, 0, data2, 0, pos);

              data2[pos] = value;

              System.arraycopy(data, pos, data2, pos + 1, (data.length - pos));

              return data2;

       }

}

interface ArrayTool {

       int[] insert(int[] data, int index, int pos, int value);

}