So basically i have this java project for school, and it requires me to read information from a text file, create an object from that information, and then insert that object into a hash table.
I am able to read the information from the text file and create the object, however, for some reason, my program isnt inserting the object into the hash table. Because then at the end of the program, when i try to search for the object (via its ID), it just returns 'not found'.
EDIT: My question is not how to compare strings. It is how to take the information from the text file, turn it into an object, and then insert it into the hash table. I know how to take the info and turn it into an object, but for some reason, it is not being inserted into the hashtable. Nothing i am inserting into the hashtable from the textfile is actually being inserted. That is the problem I am having.
This is the code i have written:
package test;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class testmain {
public static void main(String[] args) throws FileNotFoundException{
StorageSystem ss = new StorageSystem();
ss.createhashtable();
String line;
String [] parts;
File in = new File("database.txt");
Scanner sc = new Scanner(in);
while(sc.hasNextLine()){
line = sc.nextLine();
parts = line.split(" ");
String type = parts[0];
String name = parts[1];
String id = parts[2];
String price = parts[3];
if(type.equals("Insert")){
Product p1 = new Product(name, id, Double.parseDouble(price));
ss.insert(p1);
}
else if(type.equals("remove")){
ss.remove(id);
}
}
sc.close();
System.out.println(ss.searchbyID("123"));
System.out.println(ss.searchbyID("232"));
System.out.println(ss.searchbyID("444"));
System.out.println(ss.searchbyID("456"));
//If i do it manually (below), it works. But thats not the point of this project
/*
Product ex = new Product("joe", "123", 22.33);
ss.insert(ex);
System.out.println(ss.searchbyID("123"));
ss.remove("123");
System.out.println(ss.searchbyID("123"));
*/
//When i do it this way ^^, it inserts the object into the hashtable, it
//searches for the object and finds it. it then removes the object. and
//when it searches again it doesnt find anything. And thats how it
//should work.
}
}
//Below is the class that contains the information on the hashtable
import java.io.*;
import java.util.Scanner;
public class StorageSystem {
private final static int tablesize = 1000;
private static Product[] table = new Product[tablesize];
public StorageSystem(){
table = new Product[tablesize];
for(int i = 0; i < tablesize; i++){
table[i] = null;
}
}
public void createhashtable(){
table = new Product[tablesize];
for(int i = 0; i < tablesize; i++){
table[i] = null;
}
}
public void useExistingTable(Product[] pt){
table = pt;
}
public String searchbyID(String idnum){
int hash = (Integer.parseInt(idnum) % tablesize);
if(table[hash] == null){
return "Not Found.";
}
else{
Product entry = table[hash];
while((entry != null) && (entry.getID() != idnum)){
entry = entry.getNext();
}
if(entry == null){
return "Not Found.";
}
else
return entry.toString();
}
}
public void insert(Product p){
String n = p.getName();
String i = p.getID();
double pr = p.getPrice();
int hash = (Integer.parseInt(i) % tablesize);
if(table[hash] == null){
table[hash] = new Product(n, i, pr);
}
else{
Product entry = table[hash];
while((entry.getNext() != null) && (entry.getID() != i)){
entry = entry.getNext();
}
entry.setNext(new Product(n, i, pr));
}
}
public void remove(String idnum) {
int hash = (Integer.parseInt(idnum) % tablesize);
if (table[hash] != null) {
Product prevEntry = null;
Product entry = table[hash];
while (entry.getNext() != null && entry.getID() != idnum) {
prevEntry = entry;
entry = entry.getNext();
}
if (entry.getID() == idnum) {
if (prevEntry == null)
table[hash] = entry.getNext();
else
prevEntry.setNext(entry.getNext());
}
}
}
}
If anyone could help me out with this problem that would be great. I have been looking at this thing for a few days now and cant get it to work.
