lu2.java

数值分析之计算方法与实验3：线性方程组数值解法 by java

import java.io.*;
class LU2{
	public static void main(String[]args)throws IOException{
  	PrintWriter out = new PrintWriter(new FileWriter("result.txt"));
		double x1,x2,x3,x4;
		double sum=0;
		double[][] a={{48,-24,0,-12,4},{-24,24,12,12,4},{0,6,20,2,-2},{-6,6,2,16,-2}}; 
		for(int m=1;m<4;m++) a[m][0]=a[m][0]/a[0][0];    
		for(int m=1;m<4;m++){
			for(int n=1;n<5;n++){
				if(m<=n){
					for(int p=0;p<m;p++) sum=sum+a[p][n]*a[m][p];
					a[m][n]=a[m][n]-sum;
				    sum=0;
				}
				else{
					for(int p=0;p<n;p++) sum=sum+a[p][n]*a[m][p];
					a[m][n]=(a[m][n]-sum)/a[n][n];
					sum=0;
				}
			}
		}	
	x4=a[3][4]/a[3][3];      
        x3=(a[2][4]-x4*a[2][3])/a[2][2];
        x2=(a[1][4]-x4*a[1][3]-x3*a[1][2])/a[1][1];
        x1=(a[0][4]-x4*a[0][3]-x3*a[0][2]-x2*a[0][1])/a[0][0];
        
        out.println("x[1]="+x1);
        out.println("x[2]="+x2);
        out.println("x[3]="+x3);
        out.println("x[4]="+x4);
   out.close();
	}
}