java对象与类

1.设计一个用来描述汽车的类，使用类的非静态成员变量来表示汽车的车主姓名、当前的速率和当前方向盘的转向角度，使用类的非静态成员方法来表示改变汽车的速率和停车两个操作。

源代码：

package test;

public class t1 {
        private String Name;//车主姓名
        private float Speed;//当前车速
        private float Degree;//当前方向盘转向角度
        public t1(String Name){
            this.Name = Name;
        }
        public t1(String name,float speed,float degree){
            this(name);
            this.Speed = speed;
            this.Degree = degree;
        }
        public String getName(){//车主姓名访问
            return Name;
        }
        public float getDegree(){//当前方向盘转向角度访问
            return Degree;
        }
        public float getSpeed(){//当前车速访问
            return Speed;
        }
        public void changeSpeed(float Speed){//提供改变当前的车速
            this.Speed = Speed;
        }
        public void stop(){//提供停车
            this.Speed = 0;
        }
    public static void main(String[] args){
        t1 car = new t1("小明：",200f,25f);
        System.out.println("车主姓名：" +car.getName());
        System.out.println("当前车速："+car.getSpeed());
        System.out.println("当前方向盘转向角："+car.getDegree());
        car.changeSpeed(80);
        System.out.println("在调用changeSpeed(80)后，车速变为："+car.getSpeed());

2.定义一个类实现银行帐户的概念，包括的变量有"帐号"和"存款余额"，包括的方法有"存款"、"取款"、"查询余额"和”显示帐号”。定义主类，创建帐户类的对象，并完成相应操作。

源代码：

package test;
import java.util.*;
public class t3 {
    private String User;//账户
    private double Money;//当前余额
    private double add;//存款金额
    private double subtract;//取款金额
    public t3(String User){
        this.User = User;
    }
    public t3(String User,double Money){
        this(User);
        this.Money = Money;
    }
    public String getUser(){//用户账号访问
        return User;
    }
    public double getMoney(){//当前余额访问
        return Money;
    }
    public void addMoney(double Money){//存款
        this.Money+=Money;
    }
    public void subtractMoney(double Money){//取款
        this.Money-= Money;
    }
    public static void main(String[] args){
        t3 bank = new t3("12345678",34537.876);
        System.out.println("账号：" +bank.getUser());
        System.out.println("当前余额："+bank.getMoney());
        Scanner in = new Scanner(System.in);
        System.out.println("输入存款金额");
        double add = in.nextDouble();
        System.out.println("输入取款金额");
        double sub = in.nextDouble();
        bank.addMoney(add);
        System.out.println("存款后，当前余额：" +bank.getMoney());
        bank.subtractMoney(sub);
        System.out.println("取款后，当前余额："+bank.getMoney());
    }
}

 3.

设计一个类Shape（图形）包含求面积和周长的area()方法和perimeter()方法以及设置颜色的方法SetColor()，并利用Java多态技术设计其子类Circle（圆形）类、Rectangle（矩形）类和Triangle（三角形）类，并分别实现相应的求面积和求周长的方法。每个类都要覆盖toString方法。

海伦公式：三角形的面积等于s(s-a)(s-b)(s-c)的开方，其中s=(a+b+c)/2

package test;
public class t3 {
    public static void main(String[] args) {
        Circle c = new Circle(4,"white");
        System.out.println(c.toString());
        Rectangle r = new Rectangle(4, 5, "white");
        System.out.println(r.toString());
        Triangle t = new Triangle(3,4,5,"black");
        System.out.println(t.toString());
    } }
abstract class Shape{
    String color="red";
    public double area(){
        return -1;
    }
    public double perimeter(){
        return -1;
    }
    public String SetColor(String a){
        return color=a;
    }
}
class Circle extends Shape{
    private double bj;
    Circle(){
        bj=1;
    }
    Circle(double i,String col){
        bj=i;
        super.color=super.SetColor(col);
    }
    public void setBj(double b){
        this.bj = b;
    }
    public double area(){
        return Math.PI * bj * bj; }
    public double perimeter(){
        return Math.PI * bj * 2;
    }
    public String toString(){
        return( "圆的半径为" + this.bj+"圆的面积："+this.area()+"圆的周长："+this.perimeter());
    } }
class Rectangle extends Shape{
    double h;
    double w;
    Rectangle(){
    }
    Rectangle(double hi,double wi,String col){
        h=hi;
        w=wi;
        super.color=super.SetColor(col);
    }
    public double area(){
        return h * w; }
    public double perimeter(){
        return (w+h)* 2;
    }
    public String toString(){
        return( "矩形的长为" + this.h+"矩形的宽为"+this.w+"矩形的面积:"+this.area()+"矩形的周长："+this.perimeter());
    } }
class Triangle extends Shape{
    double a;
    double b;
    double c;
    Triangle(){
    }
    Triangle(double aa,double bb,double cc,String col){
        a=aa;
        b=bb;
        c=cc;
        super.color=super.SetColor(col);
    }
    public double area(){
        double s =((a+b+c)/2);
        return Math.sqrt (s*(s-a)*(s-b)*(s-c));
    }
    public double perimeter(){
        return a+b+c;
    }
    public String toString(){
        return( "三角形的长为" + this.a+"三角形的宽为"+this.b+"三角形的斜边"+this.c+"三角形的面积:"+this.area()+"三角形的周长："+this.perimeter());
    }
}