Map internal details

New key:

1. Calculate hashcode for the key
2. Calculate position hash % (arrayLength-1)) where element should be placed(bucket number)
3. If you try to add a value with a key which has already been saved in HashMap, then value gets overwritten.
4. Otherwise element is added to the bucket. If bucket has already at least one element - a new one is gets added and placed in the first position in the bucket. Its next field refers to the old element.

Deletion:

1. Calculate hashcode for the given key
2. Calculate bucket number (hash % (arrayLength-1))
3. Get a reference to the first Entry object in the bucket and by means of equals method iterate over all entries in the given bucket. Eventually we will find correct Entry. If desired element is not found - return null

put:

Step1- First of all, key object is checked for null. If key is null, value is stored in table[0] position. Because hash code for null is always 0.
Step2- Then on next step, a hash value is calculated using key’s hash code by calling its hashCode() method. This hash value is used to calculate index in array for storing Entry object. JDK designers well assumed that there might be some poorly written hashCode() functions that can return very high or low hash code value. To solve this issue, they introduced another hash() function, and passed the object’s hash code to this hash() function to bring hash value in range of array index size.
Step3- Then on next step, a hash value is calculated using key’s hash code by calling its hashCode() method. This hash value is used to calculate index in array for storing Entry object. JDK designers well assumed that there might be some poorly written hashCode() functions that can return very high or low hash code value. To solve this issue, they introduced another hash() function, and passed the object’s hash code to this hash() function to bring hash value in range of array index size.
Step4- Here comes the main part. Now, as we know that two unequal objects can have same hash code value, answer is linked list

public V put(K key, V value) {
  if (key == null)  
   return putForNullKey(value);  
  int hash = hash(key.hashCode());  
  int i = indexFor(hash, table.length);  
  for (Entry<k , V> e = table[i]; e != null; e = e.next) {
   Object k;
   if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
    V oldValue = e.value;
    e.value = value;
    e.recordAccess(this);
    return oldValue;
   }
  }

  modCount++;
  addEntry(hash, key, value, i);  
  return null;
 }

get:

public V get(Object key) {  

  if (key == null)  

   return getForNullKey();  

  int hash = hash(key.hashCode());  

  for (Entry<k , V> e = table[indexFor(hash, table.length)]; e != null; e = e.next) {  

   Object k;  

   if (e.hash == hash && ((k = e.key) == key || key.equals(k)))  

    return e.value;  

  }  

  return null;  

 }