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();    }}