数值方法LU法解线性方程组

import java.util.Scanner;

public class Gauss {
    final static int MAXN = 20;
    //static double A[][]=new double[MAXN][MAXN];
    static double L[][] = new double[MAXN][MAXN];
    static double U[][] = new double[MAXN][MAXN];
   // static double x[] = new double[MAXN];
    static double y[] = new double[MAXN];
    //static double temp[] = new double[MAXN];
    static int num;

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("输入未知数个数:");
        num = sc.nextInt();
        System.out.println("以矩阵的形式输入方程组:");
        for (int i = 0; i < num; i++) {
            for (int j = 0; j < num; j++) {
               U[i][j] = sc.nextDouble();
               L[i][j]=0;
            }
           y[i] = sc.nextDouble();
        }
//        for(int i=0;i<num;i++){
//            System.out.println(y[i]+" ");
//        }

        for (int i = 0; i < num - 1; i++) {
            handlL(i);
            handlU(i);
        }
        L[num-1][num-1]=1;
//        for(int i=0;i<num;i++){
//            for(int j=0;j<num;j++){
//                System.out.print(U[i][j]+" ");
//            }
//            System.out.println();
//        }
        for(int i=0;i<num;i++){
            jiefangchengL(i);
        }

        for(int i=num-1;i>=0;i--){
            jiefangchengU(i);
        }

        for(int i=0;i<num;i++){
            System.out.println("x"+i+"="+y[i]+" ");
        }
    }
    static  void  jiefangchengL(int ii){
        for(int i=0;i<ii;i++){
            y[ii]-=L[ii][i]*y[i];
        }
        y[ii]=y[ii]/L[ii][ii];//可有可无
    }static void jiefangchengU(int ii){
        for(int i=num-1;i>ii;i--){
            y[ii]-=U[ii][i]*y[i];
        }
        y[ii]=y[ii]/U[ii][ii];
    }
    static void handlL(int ii) {
        for (int i = num - 1; i >= ii; i--) {
            L[i][ii] =U[i][ii]/ U[ii][ii];
        }
    }

    static void handlU(int ii) {

        for (int i = ii + 1; i < num; i++) {
            double k = U[i][ii] / U[ii][ii];
            for (int j = 0; j < num; j++) {
                U[i][j] -= U[ii][j] * k;
            }
        }
    }

}