OBJECTS AND CLASSES - Introduction to Java Programming: Comprehensive Version - page 351

9.26

What is the output of the following programs?

import java.util.Date; import java.util.Date;

public class Test {
public static void main(String[] args) {
Date date = null ;
m1(date);
System.out.println(date);
}

public class Test {
public static void main(String[] args) {
Date date = new Date( 1234567 );
m1(date);
System.out.println(date.getTime());
}

public static void m1(Date date) {
date = new Date();
}
}

public static void m1(Date date) {
date = new Date( 7654321 );
}
}

(a) (b)

import java.util.Date; import java.util.Date;

public class Test {
public static void main(String[] args) {
Date date = new Date( 1234567 );
m1(date);
System.out.println(date.getTime());
}

public class Test {
public static void main(String[] args) {
Date date = new Date( 1234567 );
m1(date);
System.out.println(date.getTime());
}

public static void m1(Date date) {
date.setTime( 7654321 );
}
}

public static void m1(Date date) {
date = null ;
}
}

(c) (d)

9.11 Array of Objects
An array can hold objects as well as primitive type values.

Key
Point

Chapter 7, Single-Dimensional Arrays, described how to create arrays of primitive type ele-
ments. You can also create arrays of objects. For example, the following statement declares
and creates an array of ten Circle objects:

Circle[] circleArray = new Circle[ 10 ];

To initialize circleArray , you can use a for loop like this one:

for ( int i = 0 ; i < circleArray.length; i++) {
circleArray[i] = new Circle();
}

An array of objects is actually an array of reference variables . So, invoking circleArray[1].
getArea() involves two levels of referencing, as shown in Figure 9.19. circleArray
references the entire array; circleArray[1] references a Circle object.

Note
When an array of objects is created using the new operator, each element in the array is
a reference variable with a default value of null .