java - 我的数组元素在 Java 中具有相同的 id？

Question

这基本上是一个将两个稀疏矩阵相乘的程序。当我想设置为我的对象创建的数组的元素时，我有一个 SpEntry 类型的数组(一个具有 3 个即时变量、int row、column、value 和 getter 和 setter 方法的类)(m_1 和 m_2 是 SpArray 类的实例) & 对于每个 then 都是一个 SpEntry[] spArray，其非零元素的大小) 当我想设置每个数组的元素时，我发现 m_1[0] 和 m_1[1] (m_1 数组的元素)具有相同的 id，因此当我设置 m_1[0] 的行时， col,val m_1[1] 的 row,col,val 的元素也是重复的

public class SpArray {
    public static int N ; //size of NxN matrix
    private SpEntry[] spArray;

    public SpArray(int nNZ){
        spArray = new SpEntry[nNZ];  //nNZ is the number of Non-Zero elements of the sparse matrix

        SpEntry init = new SpEntry(0,0,0);
        for (int s=0; s<spArray.length ; s++){
            spArray[s]= init ; 

        }

    }




    //returns the spArray
    public SpEntry[] getSpArray (){
        return this.spArray;
    }




    //returns the spArray elements
        public SpEntry getSpArray (int index){
            return this.spArray[index];
        }

这是 SpArray 类的一部分 & 在主程序中:

 public static void main(String[] args) {
    int nnz_1;
    int nnz_2;
    SpArray m_1;
    SpArray m_2;


    input = new Scanner (System.in);

    System.out.println("Please enter the size of your square sparse matrix: ");
    SpArray.N = input.nextInt();

    //getting the non zero elements of the 1st sparse matrix & making its sparse array

System.out.println("请输入第一个稀疏矩阵中非零元素的个数:"); nnz_1 = input.nextInt();

    m_1 = new SpArray (nnz_1);

    for(int j_1=0; j_1<nnz_1 ; j_1++){
    System.out.println("Enter number "+ (j_1+1) + " non-zero element of the 1st sparse matrix");
        System.out.println("row: ");
        int r_1 = input.nextInt();
        System.out.println("column: ");
        int c_1 = input.nextInt();
        System.out.println("Value: ");
        int v_1 = input.nextInt();


        /*
        SpEntry e_1 = new SpEntry (r_1, c_1, v_1);
        m_1.getSpArray()[j_1].setRow(e_1.getRow());
        m_1.getSpArray()[j_1].setCol(e_1.getCol());
        m_1.getSpArray()[j_1].setVal(e_1.getVal());
        */

        //new versiin revised
        SpEntry e_1 = new SpEntry (r_1, c_1, v_1);
        m_1.getSpArray(j_1).setRow(e_1.getRow());
        m_1.getSpArray(j_1).setCol(e_1.getCol());
        m_1.getSpArray(j_1).setVal(e_1.getVal());**

    } 

当我调试程序时，它显示 m_1 数组的元素具有相同的 id(m_2 具有相同的故事):

m_1           Value: SpArray (id=21)`enter code here`
  spArray            SpEntry[2] (id=22)
    [0]              SpEntry   (id=661)
    [1]              SpEntry   (id=661)

Answer 1

您的问题在这里:

public SpArray(int nNZ){
    spArray = new SpEntry[nNZ];  //nNZ is the number of Non-Zero elements of the sparse matrix

    SpEntry init = new SpEntry(0,0,0);       // Problem here
    for (int s=0; s<spArray.length ; s++){
        spArray[s]= init ; 

    }

}

您仅创建一个对象，并使用同一对象填充整个矩阵。

如果您希望对象不同，则需要为每个元素创建一个新对象:

public SpArray(int nNZ){
    spArray = new SpEntry[nNZ];  //nNZ is the number of Non-Zero elements of the sparse matrix

    for (int s=0; s<spArray.length ; s++){
        spArray[s]= new SpEntry(0,0,0) ; 

    }

}