Wednesday, April 14, 2010

Retrieve key from HashMap using value

Below is the code to retrieve the key from HashMap using value
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;

public class TestClass {

    public static void main(String[] args) {
        Map<Integer, Person> people = new HashMap<Integer, Person>();
        Person person1 = new Person();
        Person person2 = new Person();
        people.put(1, person1);
        people.put(2, person2);

        Set<Entry<Integer, Person>> peopleSet = people.entrySet();
        for (Entry<Integer, Person> entry : peopleSet) {
            Integer key = entry.getKey();
            Person value = entry.getValue();
            if (value.equals(person2)) {
                System.out.println("Key = " + key);

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