ARRAYS - Java Programming: From Problem Analysis to Program Design - page 620

Primitive Data Types and the class Vector
As described in the preceding section, every element of a Vector object is a reference.
Therefore, to create a Vector of, say integers, the integers must be wrapped in an
object. Recall that Java provides a wrapper class corresponding to each primitive data
type. For example, the wrapper class corresponding to type int is Integer . Therefore,
an int value can be wrapped in an Integer object. As explained in Chapter 6,
as of Java 5.0, Java has simplified the wrapping and unwrapping of primitive
type values, called the autoboxing and auto-unboxing of primitive data types. For example,
suppose that x is an int variable and num is an Integer object.
Consider the statements:
num = 25;
num = new Integer(25);
After the execution of either of these statements, num would point to an Integer object
with the value 25 . Recall that the expression, num = 25; , is called the autoboxing of the
int type.
Next, we illustrate how to create a Vector of Integer objects to store int values.
Suppose that you have the declaration:
Vector<Integer> list = new Vector<Integer>();
The following statements create Integer objects with the int values 13 and 25 (if there
are no other Integer objects with these values), and the Integer objects are assigned to
list :
list.addElement(13);
list.addElement(25);
You can use other Vector operations to manipulate the objects of list . The program
IntVectorExample.java , which shows how to create and manipulate a Vector of
Integer objects, can be found with the Additional Student Files at www.cengagebrain.com.
Also, recall that the wrapper class corresponding to type char is Character , type
double is Double , type float is Float , and type boolean is Boolean .
Vector Objects and the foreach Loop
Recall that a foreach loop can be used to process the elements of a collection object one
at a time. Because each Vector object is a collection of elements, you can use a foreach
loop to process the elements of a Vector object. The syntax to use this type of for loop
to process the elements of a Vector object is:
for (type identifier : vectorObject)
statements