I want to get the key of a HashMap using the value.
hashmap = new HashMap<String, Object>();
haspmap.put("one", 100);
haspmap.put("two", 200);
Which means i want a function that will take the value 100 and will return the string one.
It seems that there are a lot of questions here asking the same thing but they don't work for me.
Maybe because i am new with java.
How to do it?
This question is related to
java
collections
hashmap
put(100, "one")
. Note that the key is the first argument, and the value is the 2nd.BiMap
(from guava)If you are not bound to use Hashmap, I would advise to use pair< T,T >. The individual elements can be accessed by first and second calls.
Have a look at this http://www.cplusplus.com/reference/utility/pair/
I used it here : http://codeforces.com/contest/507/submission/9531943
if you what to obtain "ONE" by giving in 100 then
initialize hash map by
hashmap = new HashMap<Object,String>();
haspmap.put(100,"one");
and retrieve value by
hashMap.get(100)
hope that helps.
We can get KEY
from VALUE
. Below is a sample code_
public class Main {
public static void main(String[] args) {
Map map = new HashMap();
map.put("key_1","one");
map.put("key_2","two");
map.put("key_3","three");
map.put("key_4","four");
System.out.println(getKeyFromValue(map,"four"));
}
public static Object getKeyFromValue(Map hm, Object value) {
for (Object o : hm.keySet()) {
if (hm.get(o).equals(value)) {
return o;
}
}
return null;
}
}
I hope this will help everyone.
You have it reversed. The 100 should be the first parameter (it's the key) and the "one" should be the second parameter (it's the value).
Read the javadoc for HashMap and that might help you: HashMap
To get the value, use hashmap.get(100)
.
You mixed the keys and the values.
Hashmap <Integer,String> hashmap = new HashMap<Integer, String>();
hashmap.put(100, "one");
hashmap.put(200, "two");
Afterwards a
hashmap.get(100);
will give you "one"
public class Class1 {
private String extref="MY";
public String getExtref() {
return extref;
}
public String setExtref(String extref) {
return this.extref = extref;
}
public static void main(String[] args) {
Class1 obj=new Class1();
String value=obj.setExtref("AFF");
int returnedValue=getMethod(value);
System.out.println(returnedValue);
}
/**
* @param value
* @return
*/
private static int getMethod(String value) {
HashMap<Integer, String> hashmap1 = new HashMap<Integer, String>();
hashmap1.put(1,"MY");
hashmap1.put(2,"AFF");
if (hashmap1.containsValue(value))
{
for (Map.Entry<Integer,String> e : hashmap1.entrySet()) {
Integer key = e.getKey();
Object value2 = e.getValue();
if ((value2.toString()).equalsIgnoreCase(value))
{
return key;
}
}
}
return 0;
}
}
Source: Stackoverflow.com