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}