Question

我得到了一个分配，写一个类数组和类Matrix，矩阵类将使用数组类来创建它的矩阵，它就像一个指向其他数组的数组，我的问题是一切都很好但是当我试图添加两个我创建的矩阵时，我一直有NullPointerException，这是我的整个代码。我在下面的代码中指出了我的错误，谢谢。

import java.util.Scanner;

public class Matrix {
    public Vector mat[];
    public static int m;
    static int i, j;
    Scanner sc;

    Matrix() {
        m = 0;
        mat = null;
    }

    Matrice(int m, int n) {
        Matrix.m = m;
        Vector.n = n;
        mat = new Vector[100];
        // mat[i]=new Vector(100);
    }

    public void fillmatrix() {
        mat = new Vector[100];
        sc = new Scanner(System.in);
        System.out.println("enter the number of the rows");
        Matrix.m = sc.nextInt();
        System.out.println("enter the number of your columns");
        Vector.n = sc.nextInt();
        for (j = 0; j < m; j++) {
            mat[j] = new Vector(Vector.n);
            mat[j].fillmatrix();
        }
    }

    public void DisplayMatrix() {
        System.out.println("Th matrix you have entered: ");
        for (i = 0; i < Vector.n; i++) {
            mat[i].Display();
        }

        public static Matrix Addition(Matrix mat1, Matrix mat2) {
            Matrix mat3 = new Matrix();
            for (j = 0; j < Vector.n; j++) {
                for (i = 0; i < Matrix.m; i++) {
                    mat3.mat[i].t[j] = (mat1.mat[i].t[j]) + (mat2.mat[i].t[j]); < -- -- -- -- - where the mistake but i can 't solve it ://>
                }

            }
            return mat3;
        }
    }

    public static void main(String args[]) {
        Matrix Mat1 = new Matrix();
        Matrix Mat2 = new Matrix();
        Matrix Mat3 = new Matrix();
        Mat1.fill();
        Mat1.affiche2();
        Mat2.fill();
        Mat2.affiche2();
        Mat3 = Matrix.Addition(Mat1, Mat2);
        Mat3.affiche2();
    }

    import java.util.Scanner;

    public class Vector {
        public static int n;
        static int i;
        static int j, k;
        int t[];
        static Scanner sc = new Scanner(System.in);

        Vector(int n) {
            Vector.n = n;
            t = new int[100];
        }

        Vector() {
            Vector.n = 0;
            t = null;
        }

        public void fill() {
            t = new int[100];
            sc = new Scanner(System.in);

            for (i = 0; i < n; i++) {
                System.out.println("enter " + i + "° element of your array");
                t[i] = sc.nextInt();
            }
        }

        public void contain(Vector Tab) {
            i = 0;
            j = 0;
            if (n <= Tab.t.length) {
                while (j < Tab.t.length) {
                    if (t[i] != Tab.t[j]) {
                        j++;
                        i = 0;
                    } else {
                        i++;
                        j++;
                    }
                }
                if (i > n) {
                    System.out.println("the array 1 is contained in array 2");
                }
                els
                System.out.println("the array 1is not contained in array2");
            }
        } else {
            while (i < n) {
                if (t[i] != Tab.t[j]) {
                    i++;
                    j = 0;
                } else {
                    i++;
                    j++;
                }
            }
            if (j > n) {
                System.out.println("the array 2 is contained in array 1");
            } else {
                System.out.println("the array 2 is contained in array 1");
            }
        }
    }

    boolean appartient(int x) {
        i = 0;
        boolean found = false;
        while ((i < n) && (t[i] != x)) {
            i++;
        }
        if (i >= n)
            System.out.println("le x n'appartient pas a votre Tableau");
        else {
            System.out.println("le x appartient a votre tableau");
            found = true;
        }
        return found;
    }

    public void Display() {
        for (i = 0; i < n; i++) {
            System.out.println(t[i]);
        }
    }

    public void Order() {
        int j, tmp;
        for (i = 0; i < n; i++) {
            for (j = i + 1; j < n; j++) {
                if (t[i] > t[j]) {
                    tmp = t[i];
                    t[i] = t[j];
                    t[j] = tmp;
                }
            }
        }
        for (int i = 0; i < n; i++) {
            System.out.println("your array ordered  " + t[i]);
        }
    }

    void inser(int x) {
        if (appartient(x) == true) {
            System.out.println("Insersion is impossible, the value already exist");
        } else {
            for (i = n;
                (i > 0) && (t[i - 1] > x); i--)
                t[i] = t[i - 1];

            t[i] = x;
            n++;
            for (i = 0; i < n; i++)
                System.out.println(t[i]);
        }
    }

    public static void fusionner(Vector tab1, Vector tab2) {
        Vector FUS = new Vector(tab1.t.length + tab2.t.length);
        i = 0;
        j = 0;
        k = 0;
        while ((i < tab1.t.length) && (j < tab2.t.length))
            if (tab1.t[i] < tab2.t[j]) {
                FUS.t[k] = tab1.t[i];
                k++;
                i++;
            } else {
                FUS.t[k] = tab2.t[j];
                k++;
                j++;
            }

        while (i < n) {
            FUS.t[k] = tab1.t[i];
            k++;
            i++;
        }
        while (j < n) {
            FUS.t[k] = tab2.t[j];
            k++;
            j++;
        }

        System.out.println("your arrays after the fusion is ");
        for (k = 0; k < tab1.t.length + tab2.t.length; k++)
            System.out.println(FUS.t[k]);
    }

    public static void main(String args[]) {
        Vector tab1 = new Vector();
        System.out.println("Enter n");
        n = sc.nextInt();
        tab1.fill();
        tab1.Display();
        tab1.trier();
        Vector tab2 = new Vector();
        tab2.fill();
        tab2.affiche();
        tab2.trier();
        fusionner(tab1, tab2);
        tab1.contain(tab2);
        tab2.appartient(5);
        tab1.inser(6);
    }
}

Answer 1

我决定把它作为答案而不是评论，因为它看起来很杂乱。

当您编写Matrix mat3 = new Matrix();时，您正在调用构建函数Matrix()，您将找到它，设置mat = null;。所以，只要你写一些mat3.mat[i].**something**，你就会找[null].**something**，这没有多大意义。

我推测在初始化fillmatrix()后调用mat3可能是您可能正在寻找的内容。

希望我能告诉你哪里出错了。

Answer 2

Vecteur class ..

import java.util.Scanner;
public class Matrice {

    public Vecteur mat[];
    public int m, n;
    static int i, j;
    Matrice() {
        m = 0;
        mat = null;

    }
    Matrice(int m, int n) {
        this.m = m;
        this.n = n;

        mat = new Vecteur[n];
        for (int i = 0; i < n; i++) {
            mat[i] = new Vecteur(m);
        }
    }
    Scanner sc = new Scanner(System.in);

    public void remplir() {
        mat = new Vecteur[m];

        for (j = 0; j < m; j++) {
            mat[j] = new Vecteur(this.n);
            mat[j].remplir();
        }
        public void affiche2() {
            System.out.println("L'affichage de votre matrice");

            for (j = 0; j < this.m; j++) {
                System.out.println("La ligne" + j);

                mat[j].affiche();

            }
        }

        public static void main(String args[]) {
            Scanner sc = new Scanner(System.in);
            Matrice Mat1 = new Matrice(100, 100);

            System.out.println("donner le nombre de votre Ligne a lire de la      matrice1");
            Mat1.m = sc.nextInt();
            System.out.println("donner le nombre de votre Colomne a lire de la matrice1");
            Mat1.n = sc.nextInt();
            Mat1.remplir();
            Mat1.affiche2();

            Matrice Mat2 = new Matrice(100, 100);
            System.out.println("donner le nombre de votre Ligne a lire de la matrice2");
            Mat2.m = sc.nextInt();
            System.out.println("donner le nombre de votre Colomme a lire de la matrice2");
            Mat2.n = sc.nextInt();

            Matrice Mat3 = new Matrice(100, 100);

            Mat2.remplir();
            Mat2.affiche2();

            Mat3 = Matrice.somme(Mat1, Mat2);
            Mat3.affiche2();
        }
        public static Matrice somme(Matrice mat1, Matrice mat2) {
            Matrice mat3 = new Matrice(mat1.m, mat1.n);

            for (int j = 0; j < mat1.n; j++) {
                for (int i = 0; i < mat1.m; i++) {
                    mat3.mat[i].t[j] = (mat1.mat[i].t[j]) + (mat2.mat[i].t[j]);
                }

            }

            return mat3;
        }

    }
}

Matrix class ..

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使用数组创建矩阵

2 个答案: