ch3_2.java

Java环境下实现的数值分析程序

class ch3_2{
	public static void main(String[]args){
		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}}; //创建增广矩阵
		for(int m=1;m<4;m++) a[m][0]=a[m][0]/a[0][0];     //对矩阵进行LU分解
		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];      //求解同解三角矩阵
        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];
        
        if(x1<0)System.out.println("x1="+x1); //这里的if判断仅仅是为了输出时较好看
        else System.out.println("x1= "+x1);
        if(x2<0)System.out.println("x2="+x2);
        else System.out.println("x2= "+x2);
        if(x3<0)System.out.println("x3="+x3);
        else System.out.println("x3= "+x3);
        if(x4<0)System.out.println("x4="+x4);
        else System.out.println("x4= "+x4);
	}
}