The compute(Key, BiFunction) method of Properties class allows to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping is found).
- If the remapping function passed in compute() of Properties returns null as a return value then the mapping is removed from Properties(or remains absent if initially absent).
- If the remapping function throws an exception, the exception is rethrown, and the current mapping is left unchanged.
- During computation, modification this map using this method is not allowed.
- This method will throw a ConcurrentModificationException if the remapping function modified this map during computation.
Syntax:
public Object compute?(Object key,
BiFunction remappingFunction)
Parameters: This method accepts two parameters:
- key: key with which the value is to be associated.
- remappingFunction: function to do the operation on value.
Returns: This method returns new value associated with the specified key, or null if none.
Exception: This method throws ConcurrentModificationException if it is detected that the remapping function modified this map.
Below programs illustrate the compute(Key, BiFunction) method:
Program 1:
// Java program to demonstrate// compute(Key, BiFunction) method.  import java.util.*;  public class GFG {      // Main method    public static void main(String[] args)    {          // Create a properties and add some values        Properties properties = new Properties();        properties.put("Pen", 10);        properties.put("Book", 500);        properties.put("Clothes", 400);        properties.put("Mobile", 5000);          // print Properties details        System.out.println("Current Properties: "                           + properties.toString());          // remap the values of Properties        // using compute method        properties.compute("Pen", (key, val)                                      -> 15);        properties.compute("Clothes", (key, val)                                          -> 120);          // print new mapping        System.out.println("New Properties: "                           + properties.toString());    }} |
Output:
Current Properties: {Book=500, Mobile=5000, Pen=10, Clothes=400}
New Properties: {Book=500, Mobile=5000, Pen=15, Clothes=120}
Program 2:
// Java program to demonstrate// compute(Key, BiFunction) method.  import java.util.*;  public class GFG {      // Main method    public static void main(String[] args)    {          // Create a properties and add some values        Properties properties = new Properties();          properties.put(1, "100RS");        properties.put(2, "500RS");        properties.put(3, "1000RS");          // print Properties details        System.out.println("Current Properties: "                           + properties.toString());          // remap the values of Properties        // using compute method        properties.compute(3, (key, val)                                  -> "00RS");        properties.compute(2, (key, val)                                  -> "$");          // print new mapping        System.out.println("New Properties: "                           + properties.toString());    }} |
Output:
Current Properties: {3=1000RS, 2=500RS, 1=100RS}
New Properties: {3=00RS, 2=$, 1=100RS}
