Concurrent BInarySearchTree program

Question

i am trying to make this BinarySearchTree program concurrent, i am new to concurrency so what i have done already might not work,
Also i am running it through a test program, which test for concurrency, and it is saying there is a problem in the Insert(Tree_node N, Object x) method.
Just wondered whether anybody new anything about either of these problems!!!
cheers
import java.io.*;
import java.util.*;
import java.lang.*;
class BinarySearchTree{
volatile private Tree_node root;
public void BinarySearchTree() { root = null; }
boolean isEmpty(){
if(root == null)
return true;
else
return false;
boolean insert(Object x){
if(isEmpty()){
root = new Tree_node(x, null, null);
return true;
else if(search(x)){return false;}
else{synchronized(this){
insert(root, x);}
return true;}
private void insert(Tree_node N, Object x){
if( ((Comparable)x).compareTo((Comparable)N.getData())<0 ){
if(N.getLeft() == null) {N.setLeft(new Tree_node(x, null, N));}
else{System.out.println("pass");synchronized(this){insert(N.getLeft(), x);}}
else{
if(N.getRight() == null){ N.setRight(new Tree_node(x, N, null));}
else{System.out.println("pass2"); synchronized(this){insert(N.getRight(), x);}}
boolean search(Object x){
boolean a;
if(root.isEmpty()){ a = false; return a;}
else{a = search(root, x);return a;}
private boolean search(Tree_node N, Object x){
if(N == null)return false;
if( ((Comparable)x).compareTo((Comparable)N.getData()) == 0 ){return true;}
if ( ((Comparable)x).compareTo((Comparable)N.getData()) <0 ){
return search(N.getLeft(), x);}
else{         
return search(N.getRight(), x);
boolean delete(Object x){
if(isEmpty()){return false;}
else{root = delete(root, x);
    return true;}
private Tree_node delete(Tree_node N, Object x){
if( (N.getData().equals(x)) ){
if(N.getLeft()== null && N.getRight() == null){return null;}
if(N.getLeft() == null) {return N.getRight();}
if(N.getRight() == null) {return N.getLeft();}
else {Tree_node reg = smallest_node(N.getRight());
       N.setData(reg.getData());
       N.setRight(delete(N.getRight(), reg.getData()));
       return N;}
else if( ((Comparable)x).compareTo((Comparable)N.getData()) <0){
N.setLeft(delete(N.getLeft(), x));
return N;}
else{
N.setRight(delete(N.getRight(), x));
return N;}
private Tree_node smallest_node(Tree_node N){
if(N.getLeft() == null) return N;
else {return smallest_node(N.getLeft());}
public static void main(String args[]){
/* Integer x = new Integer(4);
Integer y = new Integer(5);
Integer z = new Integer(6);
Integer a = new Integer(1);
Integer b = new Integer(2);
Integer c = new Integer(3);
Tree_node test = new Tree_node(null,null,null);
test.insert(x);
test.insert(y);
test.insert(z);
test.insert(a);
test.insert(b);
test.insert(c);
test.delete(c);
System.out.println("pass");
test.delete(x);
System.out.println("done");*/
}//end of main
}//end of class
import java.io.*;
import java.util.*;
import java.lang.*;
public class Tree_node extends BinarySearchTree{
private Object data;
private Tree_node left, right;
public Tree_node(Object d, Tree_node l, Tree_node r) {
data = d;
left = l;
right = r;
synchronized public Object getData() {return data;}
synchronized public Tree_node getLeft() {return left;}
synchronized public Tree_node getRight() {return right;}
synchronized public void setData(Object x) { data = x; }
synchronized public void setLeft(Tree_node l) {left = l;}
synchronized public void setRight(Tree_node r) {right = r;}
}//end of class
Edited by: SammyR on Mar 12, 2008 4:36 PM

Answer 1

Shell scripts are very hard to develop and maintain. Many things that developers previously had to do in shell scripts, developers can now do in PL/SQL. Hence, I recommend that you avoid shell scripts as much as possible.
As well, SQL*Loader is an old, inflexible tool. Instead, define your OS file as an external table, and then extract from the external table using a normal select statement. http://www.orafaq.com/node/848 I recommend that you avoid SQL*Loader and use external tables instead.
Using PL/SQL and external tables - and avoiding the shell script and SQL*Loader - a much better way to accomplish the same thing all inside one packaged procedure that is registered as a concurrent program:
- initialize
- select from the external table
- manipulate the data