java - 在Java中复制对象

Question

所以我的任务是研究一种基于随机突变爬山的算法。我有一种方法 RMHC，它接受一个权重 ArrayList 和两个 int，一个用于权重数量，另一个用于迭代。我的指示告诉我创建一个初始解决方案，复制它，然后将突变方法 SmallChange() 应用于初始解决方案。我还了解到如何使用 ScalesSolution 类中的 GetSol() 方法复制解决方案。该突变采用二进制字符串值(即 11101)并将二进制中的随机子字符串更改为 0 或 1 所以我可能是如果第二个子字符串发生突变，则会遇到诸如 10101 之类的输出。

我的问题是，当我对解决方案进行 SmallChange() 时，它也会对原始解决方案进行更改。

我已经尝试按照我发现的另一个问题中的建议添加复制构造函数，但它不起作用。

主要方法

public class Worksheet9 {
public static void main(String[] args) {

    ArrayList<Double> myArray = new ArrayList<Double>();

    myArray.add(1.0);
    myArray.add(2.0);
    myArray.add(3.0);
    myArray.add(4.0);
    myArray.add(10.0);

    RMHC(myArray, 5, 2);
}

RMHC方法

public static ScalesSolution RMHC(ArrayList<Double> weights,int n,int iter)
{

    ScalesSolution oldsol = new ScalesSolution(n);
    ScalesSolution newsol = new ScalesSolution(oldsol.GetSol());
    //Attempting Copy Constructor
    ScalesSolution newsol = new ScalesSolution(oldsol);



    double origfitness = oldsol.ScalesFitness(weights);
    System.out.println("Original Fitness: " + origfitness);
    double origfitness1 = newsol.ScalesFitness(weights);
    System.out.println("Cloned Original Fitness: " + origfitness1);
    newsol.SmallChange();
    double origfitness2 = newsol.ScalesFitness(weights);
    System.out.println("Changed Fitness: " + origfitness2);
    double origfitness3 = oldsol.ScalesFitness(weights);
    System.out.println("Cloned Original Fitness: " + origfitness3);

    return(oldsol);
}



}

ScalesSolution 类

import java.util.ArrayList;
import java.util.Random;

public class ScalesSolution
{
private static String scasol;
//Creates a new scales solution based on a string parameter
//The string parameter is checked to see if it contains all zeros     and ones
//Otherwise the random binary string generator is used (n = length of parameter)
#


  public ScalesSolution(ScalesSolution another) {
    this.scasol = another.scasol; // you can access  
  }




public void SmallChange() {

    int n = scasol.length();
    String s = scasol;



    Random rand = new Random();
    int p = (rand.nextInt(n));

    String x;
    x = scasol.substring(0, p);
    if (scasol.charAt(p) == '0') {
        x += '1';
    } else {
        x += '0';
    }
    x += scasol.substring(p + 1, n);
    scasol = x;

}





public String GetSol()
{
    return(scasol);
}


public ScalesSolution(String s)
{
    boolean ok = true;
    int n = s.length();
    for(int i=0;i<n;++i)
    {
        char si = s.charAt(i);
        if (si != '0' && si != '1') ok = false;
    }
    if (ok)
    {
        scasol = s;
    }
    else
    {
        scasol = RandomBinaryString(n);
    }
}
private static String RandomBinaryString(int n)
{
    String s = new String();
    //Code goes here
    //Create a random binary string of just ones and zeros of length n

    for(int i = 0; i < n; i++){
        int x = CS2004.UI(0, 1);
        if(x == 0){
            s += '0';
        } else if (x == 1) {
            s += '1';
        }
    }
    return(s);
}
public ScalesSolution(int n) 
{
    scasol = RandomBinaryString(n); 
}
//This is the fitness function for the Scales problem
//This function returns -1 if the number of weights is less than
//the size of the current solution
public static double ScalesFitness(ArrayList<Double> weights)
{
    if (scasol.length() > weights.size()) return(-1);
    double lhs = 0.0,rhs = 0.0;
    int n = scasol.length();

    for(int i = 0; i < n; i++){
        if (scasol.charAt(i) == '0') {
            lhs += weights.get(i);
            }
        else {
            rhs += weights.get(i);
        }
    }
    //Code goes here
    //Check each element of scasol for a 0 (lhs) and 1 (rhs) add the weight wi
    //to variables lhs and rhs as appropriate

    return(Math.abs(lhs-rhs));
}
//Display the string without a new line
public void print()
{
    System.out.print(scasol);
}
//Display the string with a new line
public void println()
{
    print();
    System.out.println();
}
}

当我在 main 方法中调用 RMHC 函数时，我得到如下输出:

Original Fitness: 16.0

Cloned Original Fitness: 16.0

Changed Fitness: 14.0

Cloned Original Fitness: 14.0

在此示例中，第二个克隆原始健身值也应为 16.0。一旦我弄清楚了这个初始问题，我将把代码实现到 for 循环中以包含迭代。谢谢。

Answer 1

假设这是您尝试复制数据的位置:

ScalesSolution oldsol = new ScalesSolution(n);
ScalesSolution newsol = new ScalesSolution(oldsol.GetSol());

这不起作用，因为变量是静态的:

public class ScalesSolution
{
   private static String scasol;
   //...

   public String GetSol()
   {
      return(scasol);
   }

由于您所做的只是将值分配给静态字符串 scasol，因此不会进行任何实际更改或复制。