Java程序设计上机操作与习题解析 第二章 实验1

package chapter2;

 

public class AreaAndLength {


   public static void main(String[] args) {

          double length;

          double area;

          Circle circle=null;

          Triangle triangle;

          Ladder ladder;

          circle=new Circle(2.0);

          triangle=newT riangle(3.0,4.0,5.0);

          ladder=new Ladder(3.0,5.0,7.0);

          length=circle.getLength();

          System.out.println("圆的周长是："+length);

          area=circle.getArea();

          System.out.println("圆的面积是："+area);

          length=triangle.getLength();

          System.out.println("三角形的周长是："+length);

          area=triangle.getArea();

          System.out.println("三角形的面积是："+area);

          area=ladder.getArea();

          System.out.println("梯形的面积是："+area);

          triangle.setABC(12,34, 1);

          area=triangle.getArea();

          System.out.println("三角形的面积是："+area);

          length=triangle.getLength();

          System.out.println("三角形的周长是："+length);

   }


}


package chapter2;

/**

 * 

 *
@author 23820

 
*  描述三角形

 * 具有三边，以及周长、面积

 * 功能：返回周长、返回面积、修改三边

 * 有一个boolean类型的属性，判断是否可以构成一个三角形 

 */

public class Triangle {

 

       double sideA,sideB,sideC,area,length;

       boolean boo;

       

       public Triangle(double a,double b,double c) {

              this.sideA=a;

              this.sideB=b;

              this.sideC=c;

              if(sideA+sideB>sideC&&sideA+sideC>sideB&&sideB+sideC>sideA) {

                     this.boo=true;

              }

              else  {

                     this.boo=false;

              }

       }

       

       double getLength() {

              return this.length=this.sideA+this.sideB+this.sideC;

       }

       public  double getArea() {

              if(boo){

                     double p=(sideA+sideB+sideC)/2.0;

                     area=Math.sqrt(p*(p-sideA)*(p-sideB)*(p-sideC));

                     return area;
              }

              else {

                     System.out.println("不是一个三角形，不能计算面积！");

                     return 0;

              }

       }

       public void setABC(double a,double b,double c) {

              this.sideA=a;

              this.sideB=b;

              this.sideC=c;

       }

       

}

 

package chapter2;

/**

 * 

 *
@author 23820

 
*  描述梯形

 * 上底、下底、高、面积

 * 功能：返回面积 

 */

public class Ladder {

       

       double above,bottom,height,area;

       Ladder(double a,double b,double h){

              this.above=a;

              this.bottom=b;

              this.height=h;

       }
      double  getArea() {

                     return area=(above+above)*height/2.0;

       }
}

 

package chapter2;

public class DataTypeDemo {

       public static void main(String[] args) {


              byte b=0x55;

              short s=0x55ff;

              int i=1000000;

              long l=0xffffL;

              char c='a';

              float f=0.23F;    //执行必须有F

              double d=0.7E-3;

              boolean B=true;

              String S="这是字符串数据类型";

              System.out.println("字节型变量b="+b);

              System.out.println("短整型变量s="+s);

              System.out.println("整型变量i="+i);

              System.out.println("长整型型变量l="+l);

              System.out.println("字符型变量c="+c);

              System.out.println("单精度型变量f="+f);

              System.out.println("双精度型变量d="+d);

              System.out.println("布尔型变量B="+B);

              System.out.println("字符串型变量S="+S);

       }

 

}

 

package chapter2;

/**

 * 

 *
@author 23820

 
*  描述圆形

 
*  半径、周长、面积

 * 功能：返回周长、面积

 */

public class Circle {

 

       double radius,area;

       Circle(double r){
              this.radius=r;
       }

       double getArea() {

              return area=Math.PI*radius*radius;
       }

       double getLength() {

              return Math.PI*radius*2.0;

       }

       void setRadius(double newRadius) {
              radius=newRadius;
       }

       double getRadius() {

              return radius;

       }
}