拉格朗日插值法

利用了拉格朗日插值法进行插值，代码中利用了读文件的方式，第一行为个数，第二行为X的值，第三行为Y的值，中间用空格隔开，代码如下：

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;


public class LagrangeInterpolation {
   private int n;
   private double x[];
   private double y[];
   private double l[];
   private double sum;
   public LagrangeInterpolation(int n,double[] x, double[] y) {
	 super();
	 this.n = n;
	 this.x = x;
	 this.y = y;
	 l = new double[n];
   }
   public LagrangeInterpolation(String path) {
		super();
		readFile(path);
	}
   double cal(double xx){
	   for(int i = 0;i<n;i++){
		   double ll = 1;
		   for(int j = 0;j<n;j++){
			   if(i!=j){
				   ll *= ((xx-x[j])/(x[i]-x[j]));
			   }
		   }
		   l[i] = ll*y[i];
	   }
	   double  sum = 0;
	   for(int i = 0;i<n;i++){
		   sum += l[i];
	   }
	   return sum;
   }
   void readFile(String fileName){
		 File file = new File(fileName);
	        BufferedReader reader = null;
	        try {
	            System.out.println("以行为单位读取文件内容，一次读一整行：");
	            reader = new BufferedReader(new FileReader(file));
	            String tempString = null;
	            // 一次读入一行，直到读入null为文件结束
	            if((tempString = reader.readLine())!=null){
	            	 n = Integer.parseInt(tempString);
	            }
	            x = new double[n];
	            y = new double[n];
	            l = new double[n];
	            if((tempString = reader.readLine())!=null){
	            	 String[] sourceStrArray = tempString.split(" ");
	                 for(int i=0;i<n;i++){
	                	 x[i] = Double.parseDouble(sourceStrArray[i]);
	                 } 
	            }
	            if((tempString = reader.readLine())!=null){
	            	 String[] sourceStrArray = tempString.split(" ");
	                 for(int i=0;i<n;i++){
	                	 y[i] = Double.parseDouble(sourceStrArray[i]);
	                 } 
	            }
	            reader.close();
	        } catch (IOException e) {
	            e.printStackTrace();
	        } finally {
	            if (reader != null) {
	                try {
	                    reader.close();
	                } catch (IOException e1) {
	                }
	            }
	        }
	}
	public static void main(String [] args){
		   System.out.println("请输入文件 路径"); 
	       Scanner scanner = new Scanner(System.in);  
	       String path = scanner.next();
	       LagrangeInterpolation la = new LagrangeInterpolation(path);  
	       System.out.println("请输入要求的x值");  
	       double xx = scanner.nextDouble();  
	       System.out.println(la.cal(xx));  
	       scanner.close(); 
	   }
	
}