// Deposit 1000 into John Doe's account.
double balance = tm.get("John Doe");
tm.put("John Doe", balance + 1000);
System.out.println("John Doe's new balance: " +
tm.get("John Doe"));
}
}
The following is the output from this program:
Jane Baker: 1378.0
John Doe: 3434.34
Ralph Smith: -19.08
Todd Hall: 99.22
Tom Smith: 123.22
John Doe's current balance: 4434.34
Notice that TreeMap sorts the keys. However, in this case, they are sorted by first name
instead of last name. You can alter this behavior by specifying a comparator when the map
is created, as described shortly.
The LinkedHashMap Class
LinkedHashMap extends HashMap. It maintains a linked list of the entries in the map, in the
order in which they were inserted. This allows insertion-order iteration over the map. That is,
when iterating through a collection-view of a LinkedHashMap, the elements will be returned
in the order in which they were inserted. You can also create a LinkedHashMap that returns
its elements in the order in which they were last accessed. LinkedHashMap is a generic class
that has this declaration:
class LinkedHashMap<K, V>
Here, K specifies the type of keys, and V specifies the type of values.
LinkedHashMap defines the following constructors:
LinkedHashMap( )
LinkedHashMap(Map<? extends K, ? extends V> m)
LinkedHashMap(int capacity)
LinkedHashMap(int capacity, float fillRatio)
LinkedHashMap(int capacity, float fillRatio, boolean Order)
The first form constructs a default LinkedHashMap. The second form initializes the
LinkedHashMap with the elements from m. The third form initializes the capacity. The fourth
form initializes both capacity and fill ratio. The meaning of capacity and fill ratio are the same
as for HashMap. The default capactiy is 16. The default ratio is 0.75. The last form allows
you to specify whether the elements will be stored in the linked list by insertion order, or by
order of last access. If Order is true, then access order is used. If Order is false, then insertion
order is used.
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