MyObject.java

package project1;


/*
  we store data in a way that we match some key to some value

  used like frequency arrays
  and some more complex examples
  like storing an array of indecies as a value for substring
*/
public class MyObject<K, V> {
  private static class Entry<K, V> {
    K key;
    V value;
    Entry<K, V> next;

    public Entry(K key, V value) {
      this.key = key;
      this.value = value;
    }  
  }
  private Entry<K, V>[] array_of_entries;
  private int size = 20;

  public MyObject() {
    this.array_of_entries = new Entry[size];
  }

  private int getPos(K key) {
    if (key == null) return 0;
    return Math.abs(key.hashCode()) % size; // how the key is hashed in the memory
  }

  public void set(K key, V value) {
    int idx = getPos(key);
    Entry<K, V> headEntry = array_of_entries[idx];

    while (headEntry != null) {
      if (headEntry.key.equals(key)) { // search for key like we do in LinkedList
        headEntry.value = value;
        return;
      }
      headEntry = headEntry.next;
    }

    // if not found
    Entry<K, V> newEntry = new Entry<>(key, value);
    newEntry.next = array_of_entries[idx];
    array_of_entries[idx] = newEntry;
  }

  public V get(K key) {
    int idx = getPos(key);
    Entry<K, V> headEntry = array_of_entries[idx];

    while (headEntry != null) {
      if (headEntry.key.equals(key)) {
        return headEntry.value;
      }
      headEntry = headEntry.next;
    }
    return null;
  }
}