即使在使用全局静态数组后，该数组的值也在Java中更改。 如何克服呢？

Question

In this code I am having some problem as I have marked using a loop which is printing some values. I am storing them in an array as mentioned and am trying to print the values in another function. But even after using the global array the value of the array is changing.

I am not able to figure out the problem. Please help me out.

import java.io.*;
import java.util.*;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

// Java program to print all permutations of a
// given string.
public class test3
{

    static int[] val = new int[100]    ;            //array declaration as global


    public static void main(String[] args)
    {

        System.out.println("An incremented value");
        for(int i=2;i<=2;i++) {
            String p="";
            for(int j=0;j<=i;j++) {
                for(int m=0;m<j;m++) {
                    p=p+"&";
                        }
                for(int m=0;m<i-j;m++) {
                    p=p+"|";
                        }
                 printAllPermutations(p);
                p="";
            }
        }

         System.out.println();

    for(int xy=0;xy<32;xy++)
        System.out.print("["+xy+"]"+"="+val[xy]+"   ");      //trying to print the array
    }


    static void print(char[] temp) {

        String a="";
        System.out.println();
      for (int i = 0; i < temp.length; i++)
      { System.out.print(temp[i]);
            a=a+temp[i];}

      System.out.print(" "+"opr:"+temp.length+"   ");
      final int N = temp.length+1;  

      /*===================CODE PROBLEM PART START=======================*/


      for (int i = 0; i < (1 << N); i++) {                          
        // System.out.println(zeroPad(Integer.toBinaryString(i), N));
         String b=zeroPad(Integer.toBinaryString(i), N)+"";
        // System.out.println("a:  "+a+"  b:"+b);
         char[] arrayA = b.toCharArray();
         char[] arrayB = a.toCharArray();
         StringBuilder sb = new StringBuilder();

         int ii = 0;
         while( ii < arrayA.length && ii < arrayB.length){
             sb.append(arrayA[ii]).append(arrayB[ii]);
             ++ii;
         }

         for(int j = ii; j < arrayA.length; ++j){
             sb.append(arrayA[j]);
         }

         for(int j = ii; j < arrayB.length; ++j){
             sb.append(arrayB[j]);
         }

         //System.out.println(sb.toString());
         try {
            ScriptEngineManager sem = new ScriptEngineManager();
            ScriptEngine se = sem.getEngineByName("JavaScript");
            String myExpression = sb.toString();
           // System.out.print(se.eval(myExpression));

            val[i]=(int)(se.eval(myExpression));   //inserting array value
            System.out.print(val[i]);               //NEED TO HAVE THESE VALUES IN THE 1-D ARRAY


           // System.out.print(val[i]);

         } catch (ScriptException e) {
             System.out.println("Invalid Expression");
             e.printStackTrace();}
      }  
      /*===================CODE PROBLEM PART END========================*/
     //

    }




    //unchangable = rest of the function
    static int factorial(int n) {
      int f = 1;
      for (int i = 1; i <= n; i++)
        f = f * i;
      return f;
    }

    static int calculateTotal(char[] temp, int n) {
      int f = factorial(n);

      // Building HashMap to store frequencies of 
      // all characters.
      HashMap<Character, Integer> hm = 
                       new HashMap<Character, Integer>();
      for (int i = 0; i < temp.length; i++) {
        if (hm.containsKey(temp[i]))
          hm.put(temp[i], hm.get(temp[i]) + 1);
        else
          hm.put(temp[i], 1);
      }

      // Traversing hashmap and finding duplicate elements.
      for (Map.Entry e : hm.entrySet()) {
        Integer x = (Integer)e.getValue();
        if (x > 1) {
          int temp5 = factorial(x);
          f = f / temp5;
        }
      }
      return f;
    }

    static void nextPermutation(char[] temp) {

      // Start traversing from the end and
      // find position 'i-1' of the first character 
      // which is greater than its  successor. 
      int i;
      for (i = temp.length - 1; i > 0; i--)
        if (temp[i] > temp[i - 1])
          break;

      // Finding smallest character after 'i-1' and
      // greater than temp[i-1]
      int min = i;
      int j, x = temp[i - 1];
      for (j = i + 1; j < temp.length; j++)
        if ((temp[j] < temp[min]) && (temp[j] > x))
          min = j;

      // Swapping the above found characters.
      char temp_to_swap;
      temp_to_swap = temp[i - 1];
      temp[i - 1] = temp[min];
      temp[min] = temp_to_swap;

      // Sort all digits from position next to 'i-1'
      // to end of the string.
      Arrays.sort(temp, i, temp.length);

      // Print the String
      print(temp);
    }

    static void printAllPermutations(String s) {

      // Sorting String
      char temp[] = s.toCharArray();
      Arrays.sort(temp);

      // Print first permutation
      print(temp);

      // Finding the total permutations
      int total = calculateTotal(temp, temp.length);
      for (int i = 1; i < total; i++)
        nextPermutation(temp);
    }

    static String zero(int L) {                                      
          return (L <= 0 ? "" : String.format("%0" + L + "d", 0));      
       }                                                               
    static String zeroPad(String s, int L) {                        
          return zero(L - s.length()) + s;                              
       } 

}

The output that I am getting is

 An incremented value

      || opr:2   01111111     //WANT TO STORE THESE 32 VALUES IN 1 D ARRAY 
      &| opr:2   01010111      // AND PRINT THEM OUT 
      |& opr:2   00011111     
      && opr:2   00000001      

[0]=0   [1]=0   [2]=0   [3]=0   [4]=0   [5]=0   [6]=0   [7]=1   [8]=0   [9]=0   [10]=0   [11]=0   [12]=0   [13]=0   [14]=0   [15]=0   [16]=0   [17]=0   [18]=0   [19]=0   [20]=0   [21]=0   [22]=0   [23]=0   [24]=0   [25]=0   [26]=0   [27]=0   [28]=0   [29]=0   [30]=0   [31]=0 

what I need to do is to store those 32 values in 1 D array for further operation but while doing it all the array values displays 0 only except [7]. I dont know whats going on here.

Answer 1

Reference types are not bound to local scopes, just because your array is static to the class it does not mean that changing the values in one function will not change the values in the actual array. The reference to your array as a parameter will be a copy, but the reference is still "pointing" on an actual object, which is not a copy bound to your local scope.

If you want to save two different states of the array, you will have to save them yourself.