Map.Entry : setValue : Replaces the value corresponding to this entry

V setValue(V value)

Replaces the value corresponding to this entry with the specified value. Return old value corresponding to the entry.

import java.util.*;

class MapEntrySetValue{
  public static void main(String args[]){
         Map<Integer, String> myMap = new HashMap<> ();
  
  /* Put the data to Map */
  myMap.put(1, "First");
  myMap.put(2, "Second");
  myMap.put(3, "Third");
  myMap.put(4, "Fourth");
  
  System.out.println("Before Setting");
  System.out.println("Key\tValue");
  for(Map.Entry<Integer, String> entry : myMap.entrySet()){
  System.out.println(entry.getKey()+"\t" + entry.getValue());
  }
  
  System.out.println("\nAfter Setting");
  System.out.println("Key\tValue");
  for(Map.Entry<Integer, String> entry : myMap.entrySet()){
  entry.setValue("default");
  System.out.println(entry.getKey()+"\t" + entry.getValue());
  }
  }
}

Output

Before Setting
Key     Value
1       First
2       Second
3       Third
4       Fourth

After Setting
Key     Value
1       default
2       default
3       default
4       default

1. throws UnsupportedOperationException if the put operation is not supported by the backing map

import java.util.*;

class MapEntrySetValueUnsupported{
  public static void main(String args[]){
         Map<Integer, String> myMap = new HashMap<> ();
  Map<Integer, String> unmodifiable;
  
  /* Put the data to Map */
  myMap.put(1, "First");
  myMap.put(2, "Second");
  myMap.put(3, "Third");
  myMap.put(4, "Fourth");
  
  unmodifiable = Collections.unmodifiableMap(myMap);
  for(Map.Entry<Integer, String> entry : unmodifiable.entrySet()){
  entry.setValue("default");
  System.out.println(entry.getKey()+"\t" + entry.getValue());
  }
  }
}

Output

Exception in thread "main" java.lang.UnsupportedOperationException
      at java.util.Collections$UnmodifiableMap$UnmodifiableEntrySet$Unmodifiab
leEntry.setValue(Collections.java:1488)
      at MapEntrySetValueUnsupported.main(MapEntrySetValueUnsupported.java:17)

2. throws ClassCastException if the class of the specified value

prevents it from being stored in the backing map

3. throws NullPointerException if the backing map does not permit

null values, and the specified value is null

4. throws IllegalArgumentException if some property of this value prevents it from being stored in the backing map

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