Question

I get stack overflow error when I try to load(). I am trying to read PhoneBookEntry objects from a txt file. The txt file has a name and number which make up the PhoneBookEntry object.

Can you please let me know what I’m doing wrong?

package HashSet;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.Scanner;

public class PhoneBook {
    int capacity = 10;
    private ArrayList<PhoneBookEntry>[] buckets;

    public PhoneBook() {
        this(10);
    }

    public PhoneBook(int size) {
        capacity = size;
        buckets = new ArrayList[size];
        for (int i = 0; i < buckets.length; i++) {
            buckets[i] = new ArrayList<PhoneBookEntry>();
        }
    }

    public int getSize() {
        int tot = 0;
        for (ArrayList<PhoneBookEntry> x : buckets)
            tot += x.size();
        return tot;
    }

    public boolean add(PhoneBookEntry entry) {
        if (contains(entry))
            return false;
        int x = Math.abs(entry.hashCode());
        buckets[x % buckets.length].add(entry);
        return true;
    }

    public void load()
    {
        InputStream is = getClass().getClassLoader().getResourceAsStream("phone.txt");
        Scanner scan = new Scanner(is);
        if (scan.hasNext())
            add(new PhoneBookEntry(scan.next());
    }
    public void bucketSize() {
        for (int i = 0; i < buckets.length; i++)
            System.out.println(i + "    " + buckets[i].size());
    }

    public boolean contains(PhoneBookEntry word) {
        int x = Math.abs(word.hashCode());
        return buckets[x % buckets.length].contains(word);
    }

    public int getCapacity() {
        return capacity;
    }

    public static void main(String[] args) {
        PhoneBook phone = new PhoneBook();
        phone.load();
    }
}

---

package HashSet;

import java.util.LinkedList;
import java.util.ListIterator;

public class PhoneBookEntry {
    String n;
    Integer nr;
    LinkedList<PhoneBookEntry> list;

    public PhoneBookEntry(String name, int number) {
        list = new LinkedList<PhoneBookEntry>();
        n = name;
        nr = number;
        list.add(new PhoneBookEntry(n, nr));
    }

    public String getN() {
        return n;
    }

    public void setN(String n) {
        this.n = n;
    }

    public Integer getNr() {
        return nr;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((n == null) ? 0 : n.hashCode());
        result = prime * result + ((nr == null) ? 0 : nr.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        PhoneBookEntry other = (PhoneBookEntry) obj;
        if (n == null) {
            if (other.n != null)
                return false;
        } else if (!n.equals(other.n))
            return false;
        if (nr == null) {
            if (other.nr != null)
                return false;
        } else if (!nr.equals(other.nr))
            return false;
        return true;
    }

    public void setNr(Integer nr) {
        this.nr = nr;
    }

    @Override
    public String toString() {
        return n + " " + nr;
    }
}

Answer 1

public PhoneBookEntry(String name, int number) {
    list = new LinkedList<PhoneBookEntry>();
    n = name;
    nr = number;
    list.add(new PhoneBookEntry(n, nr));
}

is causing an infinite recursion. You likely need a new class to put in the linked list (PhoneNumber or some such if a PhoneBookEntry can contain multiple names/numbers, otherwise ditch it.)