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i am reading data from a text file and want to store HashMap in another HashMap..
HashMap<string,HashMap<string,value>> how to store data and retrieve it? any sample code will be appreciated... thank u
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Given a HashMap, there are three ways one can copy the given HashMap to another: By normally iterating and putting it to another HashMap using put(k, v) method. Using putAll() method. Using copy constructor.
HashMap is similar to HashTable, but it is unsynchronized. It allows to store the null keys as well, but there should be only one null key object and there can be any number of null values. This class makes no guarantees as to the order of the map.
In Java, Map is an interface that maps keys to values. Sometimes it is required to implement Map of Map (nested Map). Nested Map is used in many cases, such as storing students' names with their Ids of different courses.
Example:
Creating and populating the maps
Map<String, Map<String, Value>> outerMap = new HashMap<String, HashMap<String, Value>>(); Map<String, Value> innerMap = new HashMap<String, Value>(); innerMap.put("innerKey", new Value()); Storing a map
outerMap.put("key", innerMap); Retrieving a map and its values
Map<String, Value> map = outerMap.get("key"); Value value = map.get("innerKey"); Creating two Simple Hashmaps: InnerMap and OuterMap
HashMap<String, HashMap<String, String>> outerMap = new HashMap<String, HashMap<String,String>>(); HashMap<String, String> innerMap = new HashMap<String, String>(); Populating the HashMaps
innerMap.put("InnerKey", "InnerValue"); outerMap.put("OuterKey", innerMap); Retreiving values from HashMaps
String value = ((HashMap<String, String>)outerMap.get("OuterKey")).get("InnerKey").toString(); System.out.println("Retreived value is : " + value); If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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