Java入门知识1

1. 获取标准屏幕的输入时，需导入java.util.Scanner包。

2. 主类的名称与.java的文件名需一致。

3. 文件中主类设置为public，其他类前面无需加访问级别。

4. 继承时，使用extends关键字，访问父类的成员时，使用super。

import java.util.Scanner;

class Circle
{
private double radius;

public Circle()
{
radius = 0.0;
}
public Circle( double radius0 )
{
radius = radius0;
}

public double getRadius()
{
return radius;
}

public double getArea()
{
return 3.14*radius*radius;
}

public double getLength()
{
return 2*3.14*radius;
}

public void Display()
{
System.out.println( "Radius is: " + radius );
System.out.println( "Length is: " + getLength() );
System.out.println( "Area is: " + getArea() );
}
}

class Cylinder extends Circle
{
private double height;

public Cylinder( double height0, double radius0 )
{
super( radius0 );
height = height0;
}

public double getHeight()
{
return height;
}

public double getRadius()
{
return super.getRadius();
}

public double getArea()
{
double area0 = super.getLength()*height;
double area1 = super.getArea()*2;
return area0 + area1;
}

public double getVolume()
{
return super.getArea()*height;
}

public void Display()
{
System.out.println( "Radius is: " + super.getRadius() );
System.out.println( "Height is: " + height );
System.out.println( "Area is: " + getArea() );
System.out.println( "Volume is: " + getVolume() );
}

}

public class TestCylinder
{

public static void main(String[] args)
{
Scanner sc = new Scanner( System.in );

System.out.println( "Please input radius:" );
double radius = sc.nextDouble();
System.out.println( "Please input height:" );
double height = sc.nextDouble();

Circle circle = new Circle( radius );
Cylinder cylinder = new Cylinder( height, radius );

circle.Display();
cylinder.Display();

}

}

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