The java.util.Map.entrySet() method in Java is used to create a set out of the same elements contained in the map. It basically returns a set view of the map or we can create a new set and store the map elements into them.
Syntax:
map.entrySet()
Parameters: The method does not take any parameter.
Return Value: The method returns a set having same elements as the hash map.
Below programs illustrate the java.util.Map.entrySet() Method:
Program 1: Mapping String Values to Integer Keys.
import java.util.*;
public class Map_Demo {
public static void main(String[] args)
{
Map<Integer, String> map = new HashMap<Integer, String>();
map.put( 10 , "Geeks" );
map.put( 15 , "4" );
map.put( 20 , "Geeks" );
map.put( 25 , "Welcomes" );
map.put( 30 , "You" );
System.out.println( "Initial Mappings are: " + map);
System.out.println( "The set is: " + map.entrySet());
}
}
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Output:
Initial Mappings are: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
The set is: [20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4]
Program 2: Mapping Integer Values to String Keys.
import java.util.*;
public class Map_Demo {
public static void main(String[] args)
{
Map<String, Integer> map = new HashMap<String, Integer>();
map.put( "Geeks" , 10 );
map.put( "4" , 15 );
map.put( "Geeks" , 20 );
map.put( "Welcomes" , 25 );
map.put( "You" , 30 );
System.out.println( "Initial Mappings are: " + map);
System.out.println( "The set is: " + map.entrySet());
}
}
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Output:
Initial Mappings are: {4=15, Geeks=20, You=30, Welcomes=25}
The set is: [4=15, Geeks=20, You=30, Welcomes=25]
Note: The same operation can be performed with any type of Mappings with variation and combination of different data types.
Reference: https://docs.oracle.com/javase/7/docs/api/java/util/Map.html#entrySet()