Java EnumMap put() method

The put() method of Java EnumMap class is used to associate the given value with the given key in this EnumMap.

Syntax

Parameters

key - the key with which the given value is to be associated

value - the value to be associated with the given key

Returns

This method returns the old value associated with the specified key.

This method returns old value if this map already contained a mapping for this key.
This method returns null if there was no mapping for the specified key.

Exception

NullPointerException - if the specified key is null.

Example 1

import java.util.*;
public class EnumMapPutExample1 {
     // create an enum  
   public enum Tutorial {
    Java, Python, PHP, Android, Javascript
   };
   public static void main(String[] args) {
    EnumMap< Tutorial, String> map = 
    		new EnumMap< Tutorial, String>( Tutorial.class);

    map.put(Tutorial.Java, "1");
    map.put(Tutorial.Python, "2");
    map.put(Tutorial.PHP, "3");
    map.put(Tutorial.Android, "4");
    //print the map
    System.out.println("Map: "+map);    
    String oldValue1 = map.put(Tutorial.Javascript, "5");
    String oldValue2 = map.put(Tutorial.Java, "20");
    //print the updated map
    System.out.println("Updated Map: " + map);
    System.out.println("First update returns: "+oldValue1);
    System.out.println("Second update returns: "+oldValue2);
  } 
}

Output:

Map: {Java=1, Python=2, PHP=3, Android=4}
Updated Map: {Java=20, Python=2, PHP=3, Android=4, Javascript=5}
First update returns: null
Second update returns: 1

Example 2

import java.util.*;
public class EnumMapPutExample2 {
    // create an enum  
     public enum Months {  
     January, February, March, April, May
     };  
      public static void main(String[] args) {  
      //create and populate enum map  
      EnumMap< Months, String> map = 
    		  new EnumMap< Months, String> (Months.class);
	   
      map.put(Months.January,"1");  
      map.put(Months.February,"2");  
      map.put(Months.March,"3");     
      map.put(Months.April,"4");      
      //print the map
      System.out.println("Map: "+map);    
      String oldValue1 = map.put(Months.May, "5");
      String oldValue2 = map.put(Months.March, "15");
      //print the updated map
      System.out.println("Updated Map: "+map);
      System.out.println("First update returns: "+oldValue1);
      System.out.println("Second update returns: "+oldValue2);
    }
}

Output:

Map: {January=1, February=2, March=3, April=4}
Updated Map: {January=1, February=2, March=15, April=4, May=5}
First update returns: null
Second update returns: 3

Example 3

import java.util.*;
public class EnumMapPutExample3 {
   // create an enum  
   public enum Days {
    Monday,Tuesday, Wednesday, Thursday
   };
   public static void main(String[] args) {
      EnumMap<Days, String>  map = new EnumMap<Days, String> (Days.class);
	
      map.put(Days.Monday, "1");
      map.put(Days.Tuesday, "2");
      map.put(Days.Wednesday, "3");	      
     //print the map
     System.out.println("Map: "+map);    
     String oldValue1 = map.put(Days.Thursday, "4");
     String oldValue2 = map.put(null, "9");
     //print the updated map
     System.out.println("Updated Map: " + map);
     System.out.println("First update returns: "+oldValue1);
     System.out.println("Second update returns: "+oldValue2);
   }
}

Output:

Map: {Monday=1, Tuesday=2, Wednesday=3}
Exception in thread "main" java.lang.NullPointerException
	at java.util.EnumMap.typeCheck(Unknown Source)
	at java.util.EnumMap.put(Unknown Source)
	at EnumMapPutExample3.main(EnumMapPutExample3.java:18)

Next TopicJava-enummap-remove-method

← prev next →