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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.



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

value - the value to be associated with the given key


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.


NullPointerException - if the specified key is null.

Example 1

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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

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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

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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(
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