面向对象-综合案例讲解和static关键字

定义一个长方形类,定义求周长和面积的方法，然后定义一个测试类，进行测试。

2、封装一个学生类，有姓名，有年龄，有性别，有英语成绩，数学成绩，语文成绩，封装方法，求总分，平均分，以及打印学生的信息。

 

public static void main(String[] args) {
        Student stu = new Student("张三",18,"男",88,92,96);
        System.out.println (stu.getName () +"的总分:"+ stu.getTotalScore());
        System.out.println (stu.getName ()+ "的平均分:"+ stu.getAvgScoure());
        stu.printstudentInfo ();
    }

}
class Student{
    private String name;
    private int age;
    private String gender;
    private double englishscore;
    private double mathScore;
    private double chinesescore;
    /**
     * 获取总分
     */

    public double getTotalScore(){
        return this.chinesescore+ this.englishscore + this.mathScore;
    }
    /**
     * 获取平均分
     */
    public double getAvgScoure(){
        return this.getTotalScore() /3;
    }

    public Student() {
        super();
    }

    public void printstudentInfo() {
        System.out.println ("name=" + this.name + "\t age=" + this.age+"\t gender" +gender + "\t englishScore=" + this.englishscore
                +"\t mathScore=" + this.mathScore + "\t chineseScore=" + chinesescore);
    }

    public Student(String name, int age, String gender, double englishscore, double mathScore, double chinesescore) {
        super();
        this.name = name;
        this.age = age;
        this.gender = gender;
        this.englishscore = englishscore;
        this.mathScore = mathScore;
        this.chinesescore = chinesescore;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public double getEnglishscore() {
        return englishscore;
    }

    public void setEnglishscore(double englishscore) {
        this.englishscore = englishscore;
    }

    public double getMathScore() {
        return mathScore;
    }

    public void setMathScore(double mathScore) {
        this.mathScore = mathScore;
    }

    public double getChinesescore() {
        return chinesescore;
    }

    public void setChinesescore(double chinesescore) {
        this.chinesescore = chinesescore;
    }



3、定义一个“点”(Point) x y set get类用来表示二维空间中的点。要求如下:
A可以生成具有特定坐标的点对象。
B提供可以设置坐标的方法。
C提供可以计算该点距离另一点距离的方法。
D提供可以计算三个点构成图形的面积的方法。
面积可以使用海伦公式:边长分别为a,b.c p=(a+b+c)/2
s=Math.sqrt(p(p-aX(p-b)*(p-c))

 

 

 

 

 

 

static关键字：

static修饰的变量我叫静态变呈/共享变呈/类变呈

static的特点:

1.静态变量属于某个类，而不属于某个具体的对象

2.只有静态才能访问静态，非静态变量不能够出现在静态方法中

3.访问静态成员的方式

1.类名.成员变量 ⒉.类名.成员方法

4.静态环境下不能出现this和super关键字

5.static能够修饰的成员(成员变量，成员方法，内部类)

举例

 public static void main(String[] args) { 

        StudentBean s1 = new StudentBean ("张三",18) ;
        StudentBean s2 =new StudentBean ("李四",19) ;
        StudentBean s3 = new StudentBean ("王五",20);

        s1.country ="中国";
        s2.country ="中国";
        s3.country ="中国";
        StudentBean.country = "中国";
        s1.show ();
        s2.show();
        s3.show();

    }

}

class StudentBean{

    private String name;
    private int age;
    public static String country;

    public void show(){
        System.out.println("name : " + name + " age:" + age + " country:" +country) ;
    }

    public StudentBean() {
    }

    public StudentBean(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

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