Програма за изчисляване на средна стойност
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Приложение 1. Програма за изчисляване на средна стойност. Вариант 1: методът average() не “улавя” изключения от вида NumberFormatException, хвърлени от метода parseDouble() и затова при грешка във формата на въвежданите числа програмата не завършва. import java.io.*; import java.util.*; class EssentialMath{ public static double average() throws IOException{ System.out.println("Enter numbers at the same line"); BufferedReader b=new BufferedReader(new InputStreamReader(System.in)); String s=b.readLine(); StringTokenizer st=new StringTokenizer(s); double sum=0; int numberOfValues =0; while(st.hasMoreTokens()){ String n=st.nextToken(); double num=Double.parseDouble(n); sum +=num; numberOfValues++; } double average=sum/numberOfValues; return average; } } public class FindAverage { public static void main(String[] args)throws IOException { double avg=EssentialMath.average(); System.out.println("The average value is: "+avg); } }
public static double average() throws IOException{ System.out.println("Enter numbers at the same line"); BufferedReader b=new BufferedReader(new InputStreamReader(System.in)); String s=b.readLine(); StringTokenizer st=new StringTokenizer(s); double sum=0; int numberOfValues =0; int numberOfErrors=0; while(st.hasMoreTokens()){ String n=st.nextToken(); try{ double num=Double.parseDouble(n); sum +=num; numberOfValues++; }catch(NumberFormatException e){ numberOfErrors++; System.out.println("Invalid number at position "+ (numberOfValues+numberOfErrors)+" ignored."); } } double average=sum/numberOfValues; return average; } Приложение 2. Програма за решаване уравнението на Кортевег де Вриз за три случая: 1) Начална вълна с две нива 2) Разпространение на 2 солитона 3) Формиране на ударна вълна import java.io.*; import java.util.Scanner; public class Soliton { //define constants static double mu=0.1;//dispersion parameter static double eps=0.15;//nonlinear parameter static double dx=0.4;//space step static double dt=0.1;//time step static int tmax=1000;//number of time iterations static int xmax=131;//number of x points static int pause=50;//pause before writing results public static void main(String[] args)throws FileNotFoundException { int i, j, k, number; double a1,a2,a3;//terms in brackets double time,param1=eps*dt/(3*dx),param2=mu*dt/(dx*dx*dx);//time and parameters double u[][]=new double[xmax][3]; System.out.println("Enter 1 for two-level wave; 2 for 2 solitons;"); System.out.println("3 for shock wave"); Scanner sc=new Scanner(System.in); number=sc.nextInt(); //open file to write the results PrintWriter w=new PrintWriter(new FileOutputStream("soliton.txt"),true); switch(number){ case 1: //initial two-level form for(i=0;i u[i][0]=0.5*(1-Math.tanh((i*dx-25)/5.));
//boundary conditions u[0][1]=1.; u[0][2]=1.;u[xmax-1][1]=0.; u[xmax-1][2]=0.;
break;
for(i=0;i u[i][0]=0.8*(1-Math.pow(Math.tanh(3*i*dx/12-3),2))+
0.3*(1-Math.pow(Math.tanh(4.5*i*dx/26-4.5),2)); //boundary conditions
u[0][1]=0.; u[0][2]=0.;u[xmax-1][1]=0.; u[xmax-1][2]=0.; break;
case 3: //initial form for shock-wave for(i=0;i u[i][0]=0.5*Math.sin(i*dx*2*Math.PI/((xmax-1)*dx));
//boundary conditions u[0][1]=0.; u[0][2]=0.;u[xmax-1][1]=0.; u[xmax-1][2]=0.;
break;
//write initial wave in file for(i=0; i w.print(u[i][0]+"\t"); w.println();
//first time step time=dt;
for(i=1;i a1=u[i+1][0]+u[i][0]+u[i-1][0];
a3=u[i+1][0]-u[i-1][0]; if(i>1 && i< (xmax-2)) a2=u[i+2][0]+2*u[i-1][0]-2*u[i+1][0]-u[i-2][0];
else a2=u[i-1][0]-u[i+1][0]; u[i][1]=u[i][0] - param1*a1*a3/2 - param2*a2/2;
}
//other time steps time +=dt; for(i=1;i a1=u[i+1][1]+u[i][1]+u[i-1][1]; a3=u[i+1][1]-u[i-1][1];
if(i>1 && i< (xmax-2)) a2=u[i+2][1]+2*u[i-1][1]-2*u[i+1][1]-u[i-2][1]; else a2=u[i-1][1]-u[i+1][1];
u[i][2]=u[i][0] - param1*a1*a3 - param2*a2; }
//write results in file for(k=0;k w.println();
}
for(k=0;k }
}//end of j-loop }
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