Answer:
Double value = 2.5; double sum = value + 5.7;
Yes, this works. It is shorthand for
Double value = new Double( 2.5 ); double sum = value.doubleValue() + 5.7;
Double value = 2.5; double sum = value + 5.7;
Yes, this works. It is shorthand for
Double value = new Double( 2.5 ); double sum = value.doubleValue() + 5.7;
Here is a program that creates an ArrayList of Integer references.
The arguments to add() look like int literals,
but
at runtime, the ints are autoboxed into Integer objects.
import java.util.* ;
public class WrapperExampleTwo
{
public static void main ( String[] args)
{
ArrayList<Integer> data = new ArrayList<Integer>();
// Autoboxing used here to create Integers
data.add( 1 );
data.add( 3 );
data.add( 17 );
data.add( 29 );
int sum = 0;
for ( Integer val : data )
sum += val; // Unboxing used here to extract the ints
System.out.print( "sum = " + sum );
System.out.println( );
}
}
The for-each loop visits the Integer objects one by one.
The statement
sum += val; // Unboxing used here to extract the ints
requires a primitive int to add to the sum.
Unboxing extracts the int from the Integer that val points to.
Do you think that the following fragment will work:
Double total, meal, tax;
meal = 20.00;
tax = meal*0.12;
total = meal+tax;
System.out.println("Total Cost: " + total );