OBJECT-ORIENTED THINKING - Introduction to Java Programming: Comprehensive Version - page 384

For instance, the following statement in (a) can be simplified as in (b) due to autoboxing.

Equivalent

Integer intObject = new Integer ( 2 ); Integer intObject = 2 ;

(a) (b)

autoboxing

Consider the following example:

1 Integer[] intArray = { 1 , 2 , 3 };
2 System.out.println(intArray[ 0 ] + intArray[ 1 ] + intArray[ 2 ]);

In line 1, the primitive values 1 , 2 , and 3 are automatically boxed into objects new Integer(1) ,
new Integer(2) , and new Integer(3) . In line 2, the objects intArray[0] , intArray[1] ,
and intArray[2] are automatically unboxed into int values that are added together.

10.12

✓ ✓

What are autoboxing and autounboxing? Are the following statements correct?

Check

Point

a. Integer x = 3 + new Integer( 5 );
b. Integer x = 3 ;
c. Double x = 3 ;
d. Double x = 3.0 ;
e. int x = new Integer( 3 );
f. int x = new Integer( 3 ) + new Integer( 4 );

10.13

Show the output of the following code?

public class Test {
public static void main(String[] args) {
Double x = 3.5 ;
System.out.println(x.intValue());
System.out.println(x.compareTo( 4.5 ));
}
}

10.9 The BigInteger and BigDecimal Classes
The BigInteger and BigDecimal classes can be used to represent integers or
decimal numbers of any size and precision.

Key
Point

If you need to compute with very large integers or high-precision floating-point val-
ues, you can use the BigInteger and BigDecimal classes in the java.math pack-
age. Both are immutable . The largest integer of the long type is Long.MAX_VALUE (i.e.,
9223372036854775807 ). An instance of BigInteger can represent an integer of any size.
You can use new BigInteger(String) and new BigDecimal(String) to create an
instance of BigInteger and BigDecimal , use the add , subtract , multiply , divide ,
and remainder methods to perform arithmetic operations, and use the compareTo method
to compare two big numbers. For example, the following code creates two BigInteger
objects and multiplies them.

immutable

VideoNote

Process large numbers

BigInteger a = new BigInteger( "9223372036854775807" );
BigInteger b = new BigInteger( "2" );
BigInteger c = a.multiply(b); // 9223372036854775807 * 2
System.out.println(c);