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This program illustrates default initialization of int , double , and boolean arrays.

The default values are as follows:

  • zero for all numeric values
  • false for all boolean values
  • all zero bits for char values
  • null for object references

An array with no elements ...

This program also illustrates that it is possible to have an array object in Java that has no elements. In this case, the value of the length property for the array object is 0.

Give me an example

For example, when the user doesn't enter any arguments on the command line for a Java application, the incoming String array parameter to the main method has a length value of 0.

Another example

It is also possible that methods that return a reference to an array object may sometimes return a reference to an array whose length is 0. The method mustsatisfy the return type requirement by returning a reference to an array object. Sometimes, there is no data to be used to populate the array, so the method willsimply return a reference to an array object with a length property value of 0.

Back to Question 15

Answer 14

A. Compiler Error

Explanation 14

Assigning array reference to type Object

As you learned in an earlier module, you can assign an array object's reference to an ordinary reference variable of the type Object . It is not necessary to indicate that the reference variable is a reference to anarray by appending square brackets to the type name or the variable name.

Only works with type Object

However, you cannot assign an array object's reference to an ordinary reference variable of any other type. For any type other than Object , the reference variable must be declared to hold a reference to an array objectby appending empty square brackets onto the type name or the variable name.

The first statement in the following fragment compiles successfully.

Object X = A; Superclass B = A;

However, the second statement in the above fragment produces a compiler error under JDK 1.3, which is partially reproduced below.

Ap077.java:22: incompatible types found : Subclass[]required: Superclass Superclass B = A;

Both Superclass and Object are superclasses of the array type referred to by the reference variable named A . However, because of theabove rule, in order to cause this program to compile successfully, you would need to modify it as shown below by adding the requisite empty square bracketsto the Superclass type name.

Object X = A; Superclass[]B = A;

Back to Question 14

Answer 13

C. 0 0 0 0 1 2

Explanation 13

Syntactical ugliness

As I indicated in an earlier module, when declaring a reference variable that will refer to an array object, you can place the empty square brackets next tothe name of the type or next to the name of the reference variable. In other words, either of the following formats will work.

int[][]A; int B[][];

What I may not have told you at that time is that you can place some of the empty square brackets in one location and the remainder in the other location.

Really ugly syntax

This is indicated by the following fragment, which declares a reference variable for a two-dimensional array of type int . Then it creates the two-dimensional array object and assigns the array object'sreference to the reference variable.

Questions & Answers

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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