java - StackOverflow error: How can I avoid it or turn this DFS into an iterative one? -

i'm using depth first search maze generation.

the adjacency matrix of m*n vertices traversed in random order using dfs, i'm interested in generating random route.

the thing works fine reduced number of vertices, i'm getting stackoverflow exception when using with

 graph thegraph = new graph(1000,1000); 

questions: a)how can change recursive calls iterative ones using stack?

b)is there way assign more memory method call stack?

class ij {          int i;         int j;          ij (int i,int j){             = this.i;             j= this.j;          }  }   class graph {      int m;     int n;      int adjacencymatrix[][];      arraylist <ij> orderofvisits;      graph(int m,int n){          this.m=m;         this.n=n;         adjacencymatrix=new int[m][n];          (int i=0; i<m; i++)             (int j=0;j<n;j++){                     adjacencymatrix[i][j]=-1; //mark vertices not visited             }          orderofvisits = new arraylist<ij>();      }   void dfs(int i, int j){ // i,j identifies vertex       boolean northvalid= false;      boolean southvalid= false;      boolean eastvalid = false;      boolean westvalid = false;        int inorth, jnorth;      int isouth, jsouth;      int ieast, jeast;      int iwest, jwest;       inorth=i-1;      if (!(inorth<0)) northvalid=true;       isouth=i+1;      if(!((isouth)>=m)) southvalid=true;       jeast=j+1;      if(!((jeast)>=n)) eastvalid=true;       jwest= j-1;      if (!(jwest<0)) westvalid=true;       if (adjacencymatrix[i][j]==-1){ //if vertex unvisited          adjacencymatrix[i][j]=0; //mark vertex visited         ij ij = new ij(i,j);         orderofvisits.add(ij); //add vertex visit list         system.out.println("visit i,j: " + +" " +j);            double lottery = math.random();         (int rows=i; rows<m; rows++)            (int cols=j; cols<n; cols++){           if (lottery>0.75d){             if(northvalid)             {                 dfs(inorth,j);             }              if(southvalid){                 dfs(isouth,j);             }              if(eastvalid){                 dfs(i, jeast);             }              if(westvalid){                 dfs(i,jwest);             }           }         else if (lottery<0.25d)        {              if(westvalid){                 dfs(i,jwest);             }               if(eastvalid){                 dfs(i, jeast);             }               if(southvalid){                 dfs(isouth,j);             }              if(northvalid)             {                 dfs(inorth,j);             }         }         else if ((lottery>=0.25d)&&(lottery<0.5d))        {               if(southvalid){                 dfs(isouth,j);             }               if(eastvalid){                 dfs(i, jeast);             }              if(westvalid){                 dfs(i,jwest);             }              if(northvalid){                 dfs(inorth,j);             }         }          else if ((lottery>=0.5d)&&(lottery<=0.75d))        {              if(eastvalid){                 dfs(i, jeast);             }              if(westvalid){                 dfs(i,jwest);             }              if(southvalid){                 dfs(isouth,j);             }              if(northvalid){                 dfs(inorth,j);             }         }      }   } //end nested  } //end dfs  // }   public class main {      /**      * @param args command line arguments      */     public static void main(string[] args) {         // todo code application logic here        graph thegraph = new graph(1000,1000);     thegraph.dfs(0,0);        }  } 

some pseudo code:

stack<ij> nodestovisit;  nodestovisit.push(new ij(0, 1)); nodestovisit.push(new ij(1, 0));  while (nodestovisit.count > 0) {     var ij = nodestovisit.pop();     if (visited ij)         continue;     .... mark ij visited     ... check north/south/east/west validity     list<ij> directions = new list<ij>();     if (cangonorth)         directions.add(new ij(inorth, j));     if (cangosouth)         directions.add(new ij(isouth, j));     if (cangoeast)         directions.add(new ij(i, jeast));     if (cangowest)         directions.add(new ij(i, jwest));     ... randomize list     foreach (direction in directions)        nodestovisit.push(direction); } 

basically:

• push possible directions on stack in random order
• pick top item
• go there
• repeat until stack empty (nor more nodes visited)

i don't think increasing stack limit solution problem.