抽象类

抽象类
关键字：abstract，
有抽象方法的类一定是抽象类，但是抽象类不一定有抽象方法。当抽象类里所有方法都是抽象方法，则称为接口（接口中定义的属性必须也一定是public static final 类型，即都是常量，不能修改）
由来：
不确定某个方法的具体实现细节，
将方法设置为abstract类型，则类也要设成abstract类型
抽象类特征：
1.不能被实例化
2.有抽象方法的类一定是抽象类
3.抽象类可以没有抽象方法
目的：
1.设计出父类，供子类继承，实现代码重用，同时给子类提供了模板
2. 设计类需要实现的功能（某些功能不具体），由派生类来具体实现
3. 为了保护类的数据和方法，将类设为abstract类型，
只有派生类才能创建对象
注意：
abstract只能修饰类和方法
不能和static联用
不能和private联用
案例
抽象类教师（Teacher）

子类1：MusicTeacher 继承Teacher, 实现teachProcedure()方法
子类2：softwareTeacher 继承Teacher,实现实现teachProcedure()方法
测试类1：TestMusicTeacher
测试类2：TestsoftwareTeacher
代码：
Teacher类

public abstract class Teacher {    //属性    private int id;    private String name;    private String sex;    private int age;    private String education;    private String teacherTitile;    //方法    public void startWork(int time){        System.out.println(this.name + time + "上班");    }    public void offWork(int time){        System.out.println(this.name + time + "下班");    }    public void teach(String course){        System.out.println(this.name  + "教" + course);    }    //构造方法    public Teacher(int id, String name, String sex, int age, String education,            String teacherTitile) {        super();        this.id = id;        this.name = name;        this.sex = sex;        this.age = age;        this.education = education;        this.teacherTitile = teacherTitile;    }    //get，set    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getSex() {        return sex;    }    public void setSex(String sex) {        this.sex = sex;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    public String getEducation() {        return education;    }    public void setEducation(String education) {        this.education = education;    }    public String getTeacherTitile() {        return teacherTitile;    }    public void setTeacherTitile(String teacherTitile) {        this.teacherTitile = teacherTitile;    }    abstract public void teachProcedure();    @Override    //ToString方法    public String toString() {        return "Teacher [id=" + id + ", name=" + name + ", sex=" + sex                + ", age=" + age + ", education=" + education                + ", teacherTitile=" + teacherTitile + "]";    }   }

MusicTeacher 类

public class MusicTeacher extends Teacher {    public MusicTeacher(int id, String name, String sex, int age,            String education, String teacherTitile) {        super(id, name, sex, age, education, teacherTitile);    }    @Override    public void teachProcedure() {        System.out.println("先唱歌，后弹琴");    }}

SoftwareTeacher类

public class SoftwareTeacher extends Teacher {    public SoftwareTeacher(int id, String name, String sex, int age,            String education, String teacherTitile) {        super(id, name, sex, age, education, teacherTitile);            }    @Override    public void teachProcedure() {        System.out.println("先java基础，后web");         }}

TestMusicTeacher类

public class TestMusicTeacher {    public static void main(String[] args) {        // TODO Auto-generated method stub        Teacher musicTeacher = new MusicTeacher(1, "张三", "男", 0, "音乐", "教授");        musicTeacher.startWork(9);        musicTeacher.offWork(17);        System.out.println(musicTeacher);        musicTeacher.teachProcedure();    }}

TestSoftwareTeacher 类

public class TestSoftwareTeacher {    public static void main(String[] args) {        Teacher softTeacher = new SoftwareTeacher(2, "李四", "女", 25, "软件老师", "教授");        System.out.println(softTeacher);        softTeacher.startWork(9);        softTeacher.offWork(17);        softTeacher.teachProcedure();    }}