math.java

计算方法课

import java.lang.Math.*;
public class math{
  double a=0.00001,b=6,error=0.001;
  public double f(double x){
   return Math.sin(x)/x;
 }

public double longbg(){
    double h,k,s,x,s1=0.0,s2,c1=0.0,c2,T1,T2,R1=0.0,R2;
    h=b-a;
    T1=(f(a)+f(b))*h/2;
    k=1;
W1: while(true){
  s = 0;
  x = a + h / 2;
  do {
    s = s + f(x);
    x = x + h;
  }
  while (x < b);
  T2 = (T1 + h * s) / 2;
  s2 = T2 + (T2 - T1) / 3;
  if (k == 1) {
    k = k + 1;
    h = h / 2;
    T1 = T2;
    s1 = s2;
    continue W1;
  }
  else
    c2=s2+(s2-s1)/15;
  if(k==2){
    c1 = c2;
    k = k + 1;
    h = h / 2;
    T1 = T2;
    s1 = s2;
    continue W1;
  }
  else
    R2=c2+(c2-c1)/63;
  if(k==3){
    R1=R2;
    c1=c2;
    k = k + 1;
    h = h / 2;
    T1 = T2;
    s1 = s2;
    continue W1;
  }
  else if(Math.abs(R2-R1)>=error){
    R1 = R2;
    c1 = c2;
    k = k + 1;
    h = h / 2;
    T1 = T2;
    s1 = s2;
    continue W1;
  }
  else
    break W1;
}
return(R2);
}

  public double bianbc(){//变步长算法
      double h,T1,T2,S,x;
      h=b-a;
      T1=((Math.sin(a))/a+(Math.sin(b))/b)*h/2;
      W1:while(true){
      S=0;
       x=a+h/2;
       do{
       S = S + Math.sin(x)/x;;
       x = x + h;
       }while(x<b);
       T2=(T1+h*S)/2;
       if(Math.abs(T2-T1)>=error){
       h = h / 2;
       T1 = T2;
       }
       else
       break W1;
       }
       return(T2);
     }

   public  static void main(String args[]){
    math m=new math();
    System.out.println("变步长算法值为："+m.longbg());
    System.out.println("龙贝格算法值为："+m.bianbc());
    }
}