Question

import java.util.*;


public class Algorithm {

public class Matrix{     
    private Double[][] x;
}

public static Scanner scan = new Scanner(System.in);
private static String str;

public static void read_data(Double[] degrees, Double[] l) {
    l[0] = 0.0;
    int i;
    for (i = 0; i < 9; i++) {
        str = scan.next();  //passem la primera columna
        str = scan.next();  //agafem el valor del desplaÃ§ament
        str = str.substring(0, str.length()-1); //traiem la coma
        l[i+1] = Double.parseDouble(str);

        str = scan.next();  //passem la primera columna
        str = scan.next();  //agafem el valor del desplaÃ§ament
        str = str.substring(0, str.length()-1); //traiem la coma
        degrees[i] = Double.parseDouble(str);
    }
    degrees[i] = 0.0;
}

public static void init_Matrix(Double[][] M, int i, Double[] degrees, Double[] l) {

    M[0][3] = l[i];
    M[0][0] = Math.cos(degrees[i]);
    M[0][1] = -Math.sin(degrees[i]);
    M[1][0] = Math.sin(degrees[i]);
    M[1][1] = Math.cos(degrees[i]);

    for (int k = 0; i < 4; k++) {
        for (int j = 0; j < 4; j++) {
            if (k == j && (M[k][j] == null)) M[k][j] = 1.0;
            else if(M[k][j] == null) M[k][j] = 0.0;
        }
    }
}

public static void init_Ultima_Matrix(Double[][] M, int i, Double[] l) {
    M[0][3] = l[i];
    for (int k = 0; k < 4; k++) {
        for (int j = 0; j < 4; j++) {
            if (k == j) M[k][j] = 1.0;
            else if(M[k][j] == null) M[k][j] = 0.0;
        }
    }
}

public static void init_Derivada(Double[][] M, int i, Double[] degrees) {
    M[0][0] = -Math.sin(degrees[i]);
    M[0][1] = -Math.cos(degrees[i]);
    M[1][0] = Math.cos(degrees[i]);
    M[1][1] = -Math.sin(degrees[i]);

    for (int k = 0; k < 4; k++) {
        for (int j = 0; j < 4; j++) {
            if(M[k][j] == null) M[k][j] = 0.0;
        }
    }
}

public static void init_Ultima_Derivada(Double[][] M, int i) {
    for (int k = 0; k < 4; k++) {
        for (int j = 0; j < 4; j++) {
            M[k][j] = 0.0;
        }
    }
}

public static void fulfill_Ts(Matrix[] Ts, Double[] degrees, Double[] l) {
    int i;
    for (i = 0; i < 9; i++) {
        Ts[i].x = new Double[4][4];
        init_Matrix(Ts[i].x, i, degrees, l);
    }
    init_Ultima_Matrix(Ts[i].x, i, l);

}

public static void fulfill_Ds(Matrix[] Ds, Double[] degrees) {
    int i;
    for (i = 0; i < 9; i++) {
        Ds[i].x = new Double[4][4];
        init_Derivada(Ds[i].x, i, degrees);
    }
    init_Ultima_Derivada(Ds[i].x, i);
}

private static Double[][] product(Double[][] A, Double[][] B){  
    Double suma = 0.0;  
    Double result[][] = new Double[4][4];  
    for(int i = 0; i < 4; i++){  
        for(int j = 0; j < 4; j++){  
            suma = 0.0;  
            for(int k = 0; k < 4; k++){  
                suma += A[i][k] * B[k][j];  
            }  
            result[i][j] = suma;  
        }  
    }  
    return result;  
}

private static void calc_Jacobian(Matrix[] Ts, Matrix[] Ds, int i, Double[][] jacobian) {
    Double[][] tmp;
    if (i == 0) tmp = Ds[0].x;
    else tmp = Ts[0].x;
    for (int j = 1; j < 10; j++) {
        if (j == i) tmp = product(tmp, Ds[j].x);
        else tmp = product(tmp, Ts[j].x);
    }
    jacobian[0][i] = tmp[0][3];
    jacobian[1][i] = tmp[1][3];
    jacobian[2][i] = tmp[0][0];
}

public static void main(String[] args) {
    Matrix[] Ts = new Matrix[10];
    Matrix[] Ds = new Matrix[10];
    for (int i = 0; i < 10; i++) {
        Ts[i].x = new Double[4][4];
        Ds[i].x = new Double[4][4];
    }
    Double[] degrees = new Double[10];
    Double[] l = new Double[10];
    read_data(degrees, l);
    fulfill_Ts(Ts, degrees, l);
    fulfill_Ds(Ds, degrees);

    Matrix jacobian = new Matrix();
    jacobian.x = new Double[3][9];
    for (int j=0; j<9; j++)
        calc_Jacobian(Ts, Ds, j, jacobian.x);
    //La matriu Jacobiana hauria d'estar acabada
}

}

嗯，这是我的代码。错误出现在第一行，其中表示＆＃34; Matrix jacobian = new Matrix（）;＆＃34;。我说错了吗？ Matrix的定义位于代码的开头。它说：不能访问类型为Algorithm的封闭实例。必须使用Algorithm类型的封闭实例限定分配（例如x.new A（），其中x是算法的实例）。

此外，我得到一个例外：＆＃34; Matrix [] Ts = new Matrix [10];＆＃34;。我不能声明一个元素数组Matrix吗？

非常感谢。

Answer 1

是的，试试这个：Matrix M = new Matrix();

这一个Matrix[] Ts = new Matrix[10];是有效的，但你也应该遍历数组元素并通过调用构造函数初始化它们。否则，它们将保持null值。

Answer 2

更改

public class Matrix

到

public static class Matrix

创建没有static修饰符的嵌套类会创建一个闭包，它允许您引用封闭实例的非静态成员。如果您没有声明它static，则需要一个封闭的实例（即this）来创建它，static void main()中没有。

解释闭包超出了本答案的范围，但它将是Algorithm _closure中的私有成员Matrix，它被隐式引用（与this相同），当你提到Algorithm的非静态成员。

Matrix无法解析为变量

2 个答案: