第一个自己写的小程序

import java.util.Scanner;

public class LY06 {

 public static void main(String[] args) {

  Scanner in=new Scanner(System.in);

  int LY02;

  do {

   System.out.println("                     作者：来自移动(2)班                               ");

   System.out.println("******************************************************");

   System.out.println("      1.部分图形的面积       ");       

   System.out.println("     2.部分图形的周长       ");   

   System.out.println("******************************************************");

   System.out.println("请输入代号进入栏目\n");

   int LY=in.nextInt();

   

   switch(LY) {

    case 1:

      System.out.println("                    面积公式计算器        ");

      System.out.println("******************************************************");

      System.out.println("     1.正方形的面积  5.长方形的面积    ");       

      System.out.println("     2.圆的面积   6.圆柱的面积    ");   

      System.out.println("     3.直角梯形的面积  7.椭圆的面积      ");

      System.out.println("     4.直角三角形面积  8.退到第一步    ");

      System.out.println("******************************************************");

       double a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t;

       System.out.println("请输入代号求面积\n");

       int LY01=in.nextInt();

      

        switch(LY01) {

         case 1:

          System.out.println("请输入正方形的边，然后回车\n");

                               a=in.nextDouble();

                               b=a*a;

                               System.out.println("正方形的面积为:"+b);

                               System.out.println("计算完成，请输入8返回第一步\n");

                               break;

         case 2:

          System.out.println("请输入圆的半径，然后回车\n");

                               c=in.nextDouble();

                               d=Math.PI*c*c;

                               System.out.println("圆的面积为:"+d);

                               System.out.println("计算完成，请输入8返回第一步\n");

                               break;

         case 3:

          System.out.println("请输入梯形的上底，下底，高，然后回车\n");

                               e=in.nextDouble();

                               f=in.nextDouble();

                               g=in.nextDouble();

                               h=((e+f)*g)/2;

                               System.out.println("梯形的面积为:"+h);

                               System.out.println("计算完成，请输入8返回第一步\n");

                               break;

         case 4:

          System.out.println("请输入直角三角形的下底，高，然后回车\n");

                               i=in.nextDouble();

                               j=in.nextDouble();

                               k=i*j/2;

                               System.out.println("直角三角形的面积为:"+k);

                               System.out.println("计算完成，请输入8返回第一步\n");

                               break;

         case 5:

          System.out.println("请输入长方形的长，宽，然后回车\n");

                               l=in.nextDouble();

                               m=in.nextDouble();

                               n=l*m;

                               System.out.println("长方形的面积为:"+n);

                               System.out.println("计算完成，请输入8返回第一步\n");

                               break;

         case 6:

          System.out.println("请输入圆柱的半径，高，然后回车\n");

                            o=in.nextDouble();

                            p=in.nextDouble();

                            q=Math.PI*o*o*p;

                            System.out.println("圆柱的面积为:"+q);

                            System.out.println("计算完成，请输入8返回第一步\n");

                            break;

         case 7:

          System.out.println("请输入椭圆长半轴，短半轴，然后回车\n");

                            r=in.nextDouble();

                            s=in.nextDouble();

                            t=Math.PI*r*s;

                            System.out.println("长方形的面积为:"+t);

                            System.out.println("计算完成，请输入8返回第一步\n");

                            break;

         case 8:

          System.out.println("帅哥美女们，别这么不给面子嘛?按8返回第一步哦\n");

          break;

        }

        break;

    case 2:

     System.out.println("                    周长公式计算器        ");

     System.out.println("******************************************************");

     System.out.println("     1.正方形的周长  4.长方形的周长    ");       

     System.out.println("     2.圆的周长   5.等边三角形的周长    ");   

     System.out.println("     3.梯形的周长   6.退到第一步      ");

     System.out.println("******************************************************");

     double A,B,C,D,E,F,G,H,I,J,K,L,M,N;

     System.out.println("请输入代号求周长\n");

     int LY03=in.nextInt();

     

     switch(LY03) {

      case 1:

       System.out.println("请输入正方形的边，然后回车\n");

                            A=in.nextDouble();

                            B=A*4;

                            System.out.println("正方形的周长为:"+B);

                            System.out.println("计算完成，请输入6返回第一步\n");

                            break;

      case 2:

       System.out.println("请输入圆的半径，然后回车\n");

                            C=in.nextDouble();

                            D=Math.PI*2*C;

                            System.out.println("圆的周长为:"+D);

                            System.out.println("计算完成，请输入6返回第一步\n");

                            break;

      case 3:

       System.out.println("请输入梯形的上底，下底，左腰，右腰，然后回车\n");

                            E=in.nextDouble();

                            F=in.nextDouble();

                            G=in.nextDouble();

                            H=in.nextDouble();

                            I=E+F+G+H;

                            System.out.println("梯形的周长为:"+I);

                            System.out.println("计算完成，请输入6返回第一步\n");

                            break;

      case 4:

       System.out.println("请输入长方形的长，宽，然后回车\n");

                            J=in.nextDouble();

                            K=in.nextDouble();

                            L=J*2+K*2;

                            System.out.println("长方形的周长为:"+L);

                            System.out.println("计算完成，请输入6返回第一步\n");

                            break;

      case 5:

        System.out.println("请输入三角形的边长，然后回车\n");

                          M=in.nextDouble();

                          N=M*3;

                          System.out.println("等边三角形的周长为:"+N);

                          System.out.println("计算完成，请输入6返回第一步\n");

                          break;

      case 6:

       System.out.println("帅哥美女们，别这么不给面子嘛?按6返回第一步哦\n");

       break;    

   

     }

     break;

   }

   LY02=in.nextInt();

  }while((LY02==8)||(LY02==6));

 }

}