编写一个Rect类 在线等

Question

要求：
（1）Rect 类的私有成员变量有：
a:double型，代表长
b:double型，代表宽
（2）Rect类的公有成员方法有：
Rect()：构造方法。默认的a、b值都是0
Rect(double len,double width):分别用两个形式参数len、width对成员变量a、b进行初始化
double area():计算矩形的面积
void display()：输出矩形的长、宽、面积
（3）然后编写一个含有main()方法的类UseRect，创建Rext类的对象，并调用上面定义的方法

Answer 1

class Rect {
private double a;
private double b;

public Rect() {
this.a = 0;
this.b = 0;
}

public Rect(double len,double width) {
this.a = len;
this.b = width;
}

public double area() {
return a*b;
}

void display() {
System.out.println("长方形的长:"+a+"长方形的宽："+b);
System.out.println("长方形的面积："+area());
}
}
public class UseRect {
public static void main(String[] args) {
Rect a = new Rect(); //默认值为0
a.area();
a.display();

Rect b = new Rect(5.0,4.0);
b.area();
b.display();
}

}

Answer 2

public class UseRect {
public static void main(String[] args) {
Rect r1=new Rect();
r1.display();
Rect r2=new Rect(5,6);
r2.display();
Rect r3=new Rect();
r3.setA(1);
r3.setB(3);
r3.display();
}
}
class Rect{
private double a;
private double b;
public Rect() {
this.a=0;
this.b=0;
}
public Rect(double len, double width) {
this.a = len;
this.b = width;
}

public double getA() {
return a;
}
public void setA(double a) {
this.a = a;
}
public double getB() {
return b;
}
public void setB(double b) {
this.b = b;
}
public double area(){
return (this.a)*(this.b);
}
public void display(){
System.out.println("a="+a+"\t"+"b="+b+"\t"+"area="+this.area());
}
}