First of all Happy New Years Eve everyone! I’m simply trying to solve 8 Queens Problem with recursive way and find all the possible answers. However, when I try to run it, Eclipse is terminating my program without any output to console. I suspect that I have problem with my recusion logic but couldn’t figure out how or why.

Here is the Queens class with main in it:

package Queens;  public class Queens {      public static void main(String[]args) {         int[][] map = new int[8][8];         int[] column = new int[8];          Problem p = new Problem();          //All possible Queen start positions send to start() method         //Column array used for storing queens column position to check         for(int i = 0; i < 8; i++) {             for(int j = 0; j < 8; j++) {                 map[i][j] = 1;                 column[j] = 1;                 p.start(map, column);                 map[i][j] = 0;                 column[j] = 0;             }         }     } } 

And Problem class, main source of work:

package Queens;  public class Problem {      public void start(int[][] mapCopy, int[] columnCopy) {         int[][] map = new int[8][8];         int[] column = new int[8];         boolean end = true;          //Copying the arrays for avoiding 'pass-by-value'         System.arraycopy(mapCopy, 0, map, 0, 8);         System.arraycopy(columnCopy, 0, column, 0, 8);          //Check for all queens placed         for(int i = 0; i < 8; i++) {             if(column[i] == 0)                 end=false;         }          //Printing answers that placed all queens right place          if(end == true) {             for(int i = 0; i < 8; i++) {                 for(int j = 0; j < 8; j++) {                     System.out.print(map[i][j] + "  ");                 }                 System.out.println();             }             System.out.println();         }          //Recursive Logic: I tried to send every possibilty to next call         //Using column[] array         for(int i = 0; i < 8; i++) {             for(int j = 0; j < 8; j++) {                 if(column[j] != 1) {                     map[i][j] = 1;                      //if a queen has right place start() method calls for next step                     //And resets remaining stuation                     //Before for loop continues for other possibilities                     if(check(map, i, j)) {                         column[j] = 1;                         start(map, column);                         column[j] = 0;                         System.out.println("lol");                     }                     else {                         map[i][j] = 0;                     }                 }             }         }     }      //Simple dimensional checks     public boolean check(int[][] mapCopy, int i, int j) {         int[][] map = new int[8][8];         int k = 0;         int l = 0;          System.arraycopy(mapCopy, 0, map, 0, 8);          for(k = 0; k < 8; k++) {             if(map[k][j] == 1)                 return false;         }          for(l = 0; l < 8; l++) {             if(map[i][l] == 1)                 return false;         }          k = i;         l = j;          for(k = i; k < 8; k++) {             if(map[k][l] == 1)                 return false;             l++;         }          k = i;         l = j;          for(k = i; 0 <= k; k--) {             if(map[k][l] == 1)                 return false;             l++;         }          k = i;         l = j;          for(k = i; k < 8; k++) {             if(map[k][l] == 1)                 return false;             l--;         }          k = i;         l = j;          for(k = i; k < 8; k--) {             if(map[k][l] == 1)                 return false;             l--;         }          return true;     } }