Menu
Java HashMap
- Generate Keys For Hashmap C Classes For Integers And Answers
- Generate Keys For Hashmap C Classes For Integers 2
- Generate Keys For Hashmap C Classes For Integers Worksheets
- Generate Keys For Hashmap C Classes For Integers 2
- Generate Keys For Hashmap C Classes For Integers Worksheet
If the hashCode function is poor and produces the same value for many keys within the HashMap, search time may degrade (The HashMap will rehash itself once the number of entries in the Map exceeds the product of the load factor and the current capacity). In a sense, HashMaps are indexed and that is what enables their good performance. Generic hashmap with String as key and Integer as value: HashMap « Collections Data Structure « Java. A) Using iterator -Before Java 5 Map map = new HashMap; map.put('a','a1'); map.put('b','b1'); Iterator itrMap = map.entrySet.iterator; while (itrMap.hasNext. Java HashMap class. Java HashMap class implements the map interface by using a hash table. It inherits AbstractMap class and implements Map interface. Points to remember. Java HashMap class contains values based on the key. Java HashMap class contains only unique keys. Java HashMap class may have one null key and multiple null values.
You learned from the previous chapter, that Arrays store items as an ordered collection, and you have to access them with an index number (
int
type). A HashMap
however, store items in 'key/value' pairs, and you can access them by an index of another type (e.g. a String
).One object is used as a key (index) to another object (value). It can store different types:
String
keys and Integer
values, or the same type, like: String
keys and String
values:Example
Create a
HashMap
object called capitalCities that will store String
keys and String
values:Add Items
The
HashMap
class has many useful methods. For example, to add items to it, use the put()
method:Access an Item
To access a value in the
HashMap
, use the get()
method and refer to its key:Example
Remove an Item
Generate Keys For Hashmap C Classes For Integers And Answers
To remove an item, use the
remove()
method and refer to the key:To remove all items, use the
clear()
method:Generate Keys For Hashmap C Classes For Integers 2
Example
Generate Keys For Hashmap C Classes For Integers Worksheets
HashMap Size
To find out how many items there are, use the
size
method:Example
Loop Through a HashMap
Generate Keys For Hashmap C Classes For Integers 2
![Generate Generate](/uploads/1/2/5/8/125872482/610349458.png)
Loop through the items of a
HashMap
with a for-each loop.Note: Use the
keySet()
method if you only want the keys, and use the values()
method if you only want the values:Example
Other Types
Keys and values in a HashMap are actually objects. In the examples above, we used objects of type 'String'. Remember that a String in Java is an object (not a primitive type). To use other types, such as int, you must specify an equivalent wrapper class:
Integer
. For other primitive types, use: Boolean
for boolean, Character
for char, Double
for double, etc:Example
Generate Keys For Hashmap C Classes For Integers Worksheet
Create a
HashMap
object called people that will store String
keys and Integer
values:Generic hashmap with String as key and Integer as value
Related examples in the same category
1. | Iterate through the values of Java HashMap example |
2. | Get Synchronized Map from Java HashMap example |
3. | Check if a particular key exists in Java HashMap example |
4. | Check if a particular value exists in Java HashMap example |
5. | Get Set view of Keys from Java HashMap example |
6. | Get Size of Java HashMap |
7. | Remove all values from Java HashMap example |
8. | Remove value from Java HashMap |
9. | Create Java Hashtable from HashMap |
10. | Sort an HashMap based on the keys |
11. | For keys of a map |
12. | For values of a map |
13. | For both the keys and values of a map |
14. | Storing Primitive Types in a Collection |
15. | Creating a Copy of a Collection: the objects are not cloned. |
16. | Use Iterator to loop through the map key set |
17. | Get key set and value set from map and use Iterator to loop through them |
18. | Clones a map |
19. | Hash map for counting references to Object keys. |
20. | Extended Version of java.util.HashMap that provides an extended get method accpeting a default value. |
21. | Compact HashMap |
22. | This class wraps a HashMap and provides methods by which key objects can be associated with 'counting' values. |
23. | This extension of HashMap support duplicate keys |
24. | Concurrent Hopscotch HashMap |