View difference between Paste ID: rfrmaS6K and iP62ACde

 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.PrintWriter;
 
 import org.apache.commons.math.linear.Array2DRowRealMatrix;
 import org.apache.commons.math.linear.ArrayRealVector;
 import org.apache.commons.math.linear.DecompositionSolver;
 import org.apache.commons.math.linear.LUDecompositionImpl;
 import org.apache.commons.math.linear.RealMatrix;
 import org.apache.commons.math.linear.RealVector;
 
 
 public class Solution {
 	public final static int a=-1;
 	public final static int b=1;
 	public final static int INTEGRAL_STEP=100000;
 	public final static int lambda=1;
 	private double h;
 	private int n=1;
 	private int sum;
 	private double B[][];
 	private double d[];
 	private double c[];
 	private double eps_prev=0;
 	public double f(double x){
 		return Math.cos(4*Math.PI*x)-
 		(lambda*2*x*Math.sin(Math.PI*x))/(Math.PI*(x*x-16));
 	}
 	public double K(double x, double s){
 		return Math.cos(Math.PI*x*s);
 		//return Math.abs(x+s);
 	}
 	public double u(double x){
 		return Math.cos(4*Math.PI*x);
 		//return Math.abs(x);
 	}
 	public double ksi_0(double x){
 		if (x>=a && x<=(a+h)){
 			return (a+h-x)/h;
 		}
 		else{
 			return 0;
 		}
 	}
 
 	public double ksi_i(double x, int i){
 		if (x>=a+(i-1)*h && x<=(a+h*i)){
 			return (x-(a+(i-1)*h))/h;
 		}
 		else
 			if (x>=a+i*h && x<=(a+h*(i+1))){
 				return (x+(i+1)*h-x)/h;
 			}
 		else{
 			return 0;
 		}
 	}
 
 	public double ksi_n(double x){
 		if (x>=a+h*(n-1) && x<=(a+h*n)){
 			return (a+h-x)/h;
 		}
 		else{
 			return 0;
 		}
 	}
 	public double intergrateBij(int i, int j){
 		double sum=0;
 		double h=this.h/INTEGRAL_STEP;;
 		double x;
 
 		if (i==0){
 			for (int k=0; k<INTEGRAL_STEP;k++){
 				x=a+k*h;
 				sum+=ksi_0(x)*K(x,a+this.h*j);
 			}
 		}
 		else{
 			if (i==n){
 				for (int k=0; k<INTEGRAL_STEP;k++){
 					x=b-k*h;
 					sum+=ksi_n(x)*K(x,a+this.h*j);
 				}
 			}
 			else{
 				double x0=a+(i-1)*this.h;
 				for (int k=0; k<INTEGRAL_STEP;k++){
 					x=x0+h*k;
 					sum+=ksi_i(x,i)*K(x,a+this.h*j);
 				}
 				x0=a+i*this.h;
 				for (int k=0; k<INTEGRAL_STEP;k++){
 					x=x0+h*k;
 					sum+=ksi_i(x,i)*K(x,a+this.h*j);
 				}
 			}
 		}
 		return sum*h;
 	}
 	public double integrateDi(int i){
 		double sum=0;
 		double h=this.h/INTEGRAL_STEP;;
 		double x;
 		if (i==0){
 			for (int k=0; k<INTEGRAL_STEP;k++){
 				x=a+k*h;
 				sum+=ksi_0(x)*f(x);
 			}
 		}
 		else{
 			if (i==n){
 				for (int k=0; k<INTEGRAL_STEP;k++){
 					x=b-k*h;
 					sum+=ksi_n(x)*f(x);
 				}
 			}
 			else{
 				double x0=a+(i-1)*this.h;
 				for (int k=0; k<INTEGRAL_STEP;k++){
 					x=x0+h*k;
 					sum+=ksi_i(x,i)*f(x);
 				}
 				x0=a+i*this.h;
 				for (int k=0; k<INTEGRAL_STEP;k++){
 					x=x0+h*k;
 					sum+=ksi_i(x,i)*f(x);
 				}
 			}
 		}
 		return sum*h;
 	}
 	public void initMartix(){
 		d=new double[n+1];
 		B=new double[n+1][];
 		for (int i=0; i<n+1; i++){
 			B[i]=new double[n+1];
 		}
 		for (int i=0; i<n+1; i++){
 			for (int j=0; j<n+1; j++){
 				B[i][j]=lambda*intergrateBij(i, j);
 				if (i!=j){
 					B[i][j]=-B[i][j];
 				}
 				else{
 					B[i][j]=1-B[i][j];
 				}
 			}
 			d[i]=integrateDi(i);
 		}
 		RealMatrix coefficients=new Array2DRowRealMatrix(B);
 		DecompositionSolver solver=new LUDecompositionImpl(coefficients).getSolver();
 		RealVector constants=new ArrayRealVector(d);
 		RealVector solution=solver.solve(constants);
 		c=solution.getData();
 	}
 	public double u_wave(double x){
 		double sum=0;
 		for (int i=0; i<n+1;i++){
 			sum+=c[i]*K(x,a+i*h);
 		}
 		sum*=lambda;
 		sum+=f(x);
 		return sum;
 	}
 
 	public void solve() throws FileNotFoundException{
 		PrintWriter writer;
 		double x_i;
 		double eps_max;
 		double eps;
 		double u_1,u_2;
 		long start, finish;
 		for (int i=1; i<=10; i++){
 			System.out.println("I="+i);
 			start=System.currentTimeMillis();
 			sum=0;
 			n*=2;
 			h=(b-a)/(double)n;
 			initMartix();
 			eps_max=-1;
 			for (int j=1; j<=n; j++){
 				x_i=a+(j-1)*h;
 				u_1=u(x_i);
 				u_2=u_wave(x_i);
 				System.out.println("with u="+u_1+" and u_wave="+u_2);
 				eps=Math.abs(u_1-u_2);
 				if (eps>eps_max){
 					eps_max=eps;
 				}
 			}
 			finish=System.currentTimeMillis();
 			writer = new PrintWriter(new File("out" + i + ".txt"));
 			writer.println("h_i = "+h);
 			writer.println("eps = "+eps_max);
 			writer.println("r_i = " + Math.log((eps_prev)/eps_max)/Math.log(2));
 			eps_prev=eps_max;
 			writer.println("t_i = " + (finish-start));
 			writer.close();
 		}
 
 
 	}
 
 }