java - 将二维数组硬编码到构造函数中

Question

我目前正在尝试将预设值硬编码到构造函数中，它给了我一条“非法启动消息”。如果它不允许那很好，我想我会尝试找到解决方法。我正在开发的程序使用矩阵 1 的特定值来使程序的其余部分正常工作。我是一个初学者，所以我可能做错了。我查看了 Java API，没有发现任何内容表明我不能做我想做的事情。我有一个AssignmentOne 类，其中编码了方法和构造函数，还有一个AssignmentOneTest 来测试代码。我真的很想为此使用两个类。 下面是我的代码:

public class AssignmentOne {
private double[][] matrix1;
private double[][] matrix3;

public AssignmentOne(){
  matrix3 = new double[3][3];
  matrix1 = {{0.9,0.05,0.05},
             {0.05,0.9,0.05},
             {0.05,0.05,0.9}};

}//Constructor END

Answer 1

您只能在声明数组时对数组进行硬编码，而不能在稍后的代码中对其进行硬编码。所以这样就可以了:

public class AssignmentOne {
    double[][] matrix1 = {{0.9,0.05,0.05},
             {0.05,0.9,0.05},
             {0.05,0.05,0.9}};

    public AssignmentOne(){

        // now you are free to use matrix1 here if need be

    }

但这不是:

public class AssignmentOne {
    double[][] matrix1;

    public AssignmentOne(){
      matrix1 = {{0.9,0.05,0.05},
                 {0.05,0.9,0.05},
                 {0.05,0.05,0.9}};        
    }

另一个可行的解决方案是允许构造函数接受数组参数，并传入在其他地方初始化的数组，例如在 main 方法中:

public class AssignmentOne {
    double[][] matrix1;

    public AssignmentOne(double[][] matrix1){
       this.matrix1 = matrix1; 
    }

然后在其他地方:

public static void main(String[] args) {
    double[][] arr = {{0.9,0.05,0.05},
             {0.05,0.9,0.05},
             {0.05,0.05,0.9}};

    AssignmentOne assignmentOne = new AssignmentOne(arr);
}