如何将更新的参数值传递回它们来自的方法？

Question

我在将 initial_guess_1 和 initial_guess_2 的更新值传递回 GoldenSectionSearch 方法时遇到问题（我试图让该方法自行调用，直到与“if”相关的终止条件得到满足）。我自己解决这个问题的尝试受到了我在这里发现的影响：

https://softwareengineering.stackexchange.com/questions/286008/parameters-are-passed-by-value-but-editing-them-will-edit-the-actual-object-li

http://www.java-tutorial.com/java-tutorial/java-classes-methods/java-call-reference/

我仍然无法弄清楚我在尝试将更新的值传递回方法时做错了什么。我做错了什么，我该如何解决？我是编程新手，希望将事情分解成最小、最容易理解的术语。

public static double GoldenSectionSearch(double x_1, double x_2, double initial_guess_1,double initial_guess_2 ,double gradient_x, double gradient_y, double a,double a_0,double a_1,double a_2,double b_0,double b_1,double p,double N){

          //Stuff

         if(Math.abs((100*(x_2 - x_1*x_1)*(x_2 - x_1*x_1) + (1- x_1)*(1- x_1)) - (100*(initial_guess_2 - initial_guess_1*initial_guess_1)*(initial_guess_2 - initial_guess_1*initial_guess_1) + (1- initial_guess_1)*(1- initial_guess_1)) )/Math.abs(1+(100*(initial_guess_2 - initial_guess_1*initial_guess_1)*(initial_guess_2 - initial_guess_1*initial_guess_1) + (1- initial_guess_1)*(1- initial_guess_1))) >=0.50*Math.pow(10,-6)){

                  initial_guess_1=x_1;
                  initial_guess_2=x_2;
                  //Double Boxed_a = new Double(a);
                  Double Boxed_initial_guess_1 = new Double(initial_guess_1);
                  Double Boxed_initial_guess_2 = new Double(initial_guess_2);


                  initial_guess_1.GoldenSectionSearch(initial_guess_1);
                  initial_guess_2.GoldenSectionSearch(initial_guess_2);
                  gradient_x = (400*initial_guess_1*(initial_guess_1*initial_guess_1 - initial_guess_2) + 2*(initial_guess_1 -1));
                  gradient_y = (200*(initial_guess_2 - initial_guess_1*initial_guess_1));

                  GoldenSectionSearch(initial_guess_1,initial_guess_2,x_1, x_2, gradient_x, gradient_y, a, a_0, a_1, a_2, b_0, b_1, p,N);      


         } else{



               double f_x=(100*(x_2 - x_1*x_1)*(x_2 - x_1*x_1) + (1- x_1)*(1- x_1));
               System.out.print("alpha = " + a + "    " + "x_1 = " + x_1 + "    " + "x_2 = " + x_2 + "    " + "f_x = " + f_x);
         }



        // Double Boxed_a = new Double(a);


         return x_2; 

      }

Answer 1

您不能修改原语。您必须使用 getter/setter 创建包装类

public class MyWrapperObject {

    private double x_1;
    private double x_2;
    private double initial_guess_1;
    private double initial_guess_2;
    private double gradient_x;
    private double gradient_y;
    private double a;
    private double a_0;
    private double a_1;
    private double a_2;
    private double b_0;
    private double b_1;
    private double p;
    private double N;

    public double getX_1() {
        return x_1;
    }

    public void setX_1(double x_1) {
        this.x_1 = x_1;
    }
    /* The rest of getters/setters */
}

将其传递给您的方法并像使用它一样使用它

public static double GoldenSectionSearch(MyWrapperObject obj){
        // ...
        double initial_guess_1 = obj.get_initial_guess_1();
        double initial_guess_2 = obj.get_initial_guess_2();
        obj.setGradient_x(400*initial_guess_1*(initial_guess_1*initial_guess_1 - initial_guess_2) + 2*(initial_guess_1 -1));
        // ...
    }

这里还有一个关于java是按引用传递还是按值传递https://stackoverflow.com/a/40523/2022162的问题