Binary search tree preorder traversal

import java.io.*;
import java.util.*;




class Nodetype
{
int info;
Nodetype left;
Nodetype right;
Nodetype father;
Nodetype(int i)
{
info=i;
left=null;
right=null;
father=null;
}
}


class Stack
{
Nodetype stk[]=new Nodetype[100];
int top;
Stack()
{
top=-1;
}
void push (Nodetype item)
{
if (top==9)
System.out.println("Stack overflow");
else
stk[++top]=item;
}/*end push*/


boolean isempty()
{
if (top<0)
return true;
else
return false;
}/*end isempty*/


Nodetype pop()
{
if (isempty())
{
System.out.println("Stack underflow");
return null;
}
else
return (stk[top--]);
}/*end pop*/
}






class Functions
{


Stack s=new Stack();


Nodetype maketree(int x)
{
Nodetype node=new Nodetype(x);
return(node);
}/*end maketree*/


void setleft(Nodetype p,int x)
{
if(p==null)
System.out.println("\nInvalid insertion");
else
if(p.left!=null)
System.out.println("\nInvalid insertion");
else p.left=maketree(x);
}/*end setleft*/


void setright(Nodetype p,int x)
{
if(p==null)
System.out.println("\nInvalid insertion");
else
if(p.right!=null)
System.out.println("\nInvalid insertion");
else
p.right=maketree(x);
}/*end setright*/


void pretrav(Nodetype tree)
{
// let tree be the pointer to the beginning of tree
Nodetype p;
s.top=-1;
s.push(tree);
while (!s.isempty())
{
p=s.pop();
System.out.print(p.info+" ");
if(p.right!=null)
s.push(p.right);
if (p.left!=null)
s.push(p.left);
}
}


void create()
{
Nodetype ptree,p,q;
int n,number=0,i;
System.out.print("\nEnter number of nodes : ");
n=getNumber();
System.out.println("\nEnter info "+n+" nodes :");
number=getNumber();
ptree=maketree(number);
for(i=1;i<n;i++)
{
number=getNumber();
p=q=ptree;
while(q!=null&&number!=p.info)
{
p=q;
if(number<p.info)
 q=p.left;
else
 q=p.right;
}
if(number==p.info)
System.out.println("Sorry !....."+number+"is a duplicate\n");
else
if(number<p.info)
setleft(p,number);
else
setright(p,number);
}


System.out.println("\nPreorder  : ");
pretrav(ptree);


}


int getNumber()
{
String str;
int ne=0;
InputStreamReader input=new InputStreamReader(System.in);
BufferedReader in=new BufferedReader(input);
try
{
str=in.readLine();
ne=Integer.parseInt(str);
}
catch(Exception e)
{
System.out.println("I/O Error");
}
return ne;
}




}


class BSTTravPre
{
public static void main(String arg[])
{
Functions f=new Functions();
f.create();


}/*end main*/
}




/*




Enter number of nodes : 6


Enter info 6 nodes :
50
60
62
1
10
9


Preorder  :
50 1 10 9 60 62
*/