The outputs below are different. I don't know what's wrong and I have tried to correct many times.
There has File and Folder two java files.And for the format, for a listed folder,there must be a "/" at the end and for each folder/file, the path must be the absolute path.
The output must be
dir1/
dir1/f1/
dir1/dir2/
dir1/dir2/f3/
dir1/dir2/f4/
dir1/dir2/dir3/
dir1/dir2/dir3/f5/
dir1/f2/
However,my output is
dir1/
dir1/f1/
dir1/dir2/
dir2/f3/
dir2/f4/
dir2/dir3/
dir3/f5/
dir1/f2/
Here is my code.
public class File implements Composite {
public String name;
//private ArrayList<File>a=new ArrayList<File>();
public File(String name)
{
this.name=name;
}
public void list() {
System.out.print(name+"/");
System.out.println();
}
}
Folder.java
import java.util.ArrayList;
public class Folder implements Composite{
public String name;
public ArrayList b = new ArrayList();
public Folder(String name){
this.name=name;
}
public void add(Object o)
{
b.add(o);
}
public void list(){
int e=b.indexOf(name)+1;
System.out.println(name+"/");
Composite r=(Composite) b.get(e);
for(int i=0;i<b.size();i++) {
System.out.print(name+"/");
Composite a=(Composite)b.get(i);
a.list();
}
}
public String getName(){
return name;
}
}
In your code, you need to track the parent folder of each Folder.
So the constructor needs to be Folder(Folder parent, String name). The root (topmost) folder has null as parent.
When you print the name, you need to ask the current folder for it's path. The code for this method would be:
public String getPath() {
if(null == parent) return name;
return parent.getPath() + "/" + name;
}
Related
My Package A has one java file with 2 classes. Login class which is public and LoginDetails class which cannot be public because it is in the same file. how to create a List of LoginDetails type from Package B.
package A;
public class Login {
private String name;
private String passWord;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassWord() {
return passWord;
}
public void setPassWord(String passWord) {
this.passWord = passWord;
}
#Override
public String toString() {
return "Login [name=" + name + ", passWord=" + passWord + "]";
}
}
class LoginDetails{
public LoginDetails(int id, int geight) {
super();
this.id = id;
this.geight = geight;
}
private int id;
private int geight;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getGeight() {
return geight;
}
public void setGeight(int geight) {
this.geight = geight;
}
public void hidden() {
System.out.println("From hidden");
}
public LoginDetails() {
}
}
package B;
import java.util.ArrayList;
import java.util.List;
public class Demo {
public static void main(String[] args) throws Exception {
List<LoginDetails> l = new ArrayList<LoginDetails>();
}
}
A solution to your weird question which doesnt include changing neither of the Login nor LoginDetails classes would be by adding a second Public class called AUtils such like this:
AUtils/AFactory class
package A;
import java.util.ArrayList;
public class AUtils {
public static ArrayList<LoginDetails> generateList(){
return new ArrayList<LoginDetails>();
}
public static ArrayList<LoginDetails> generateListWithInitialSize(int x){
return new ArrayList<LoginDetails>(x);
}
public static LoginDetails generateAnObject(){
return new LoginDetails();
}
public static LoginDetails generateWithData(int id, int geight){
return new LoginDetails(id,geight);
}
}
And your Demo would look like this:
public class Demo {
public static void main(String[] args) {//plus you dont need To throw exception thus your program dont throw any!:)
List l = AUtils.generateList();
// List l = AUtils.generateListWithInitialSize(10);//will give you array list with initial size 10
l.add(AUtils.generateAnObject());//if you do so be aware that the objects would be created with 0 as id and eight.
// l.add(AUtils.generateWithData(3,3));
}
}
please be aware that this normally is not acceptable and considered as bad coding because its kinda turn around ;) so either you misunderstood the assignment or the one who wrote it is really a carrot.
happy coding.
You cannot do it directly without changing of the design or visibility of the classes.
If a class has no modifier (the default, also known as
package-private), it is visible only within its own package.
https://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html
Currently, there are 3 classes which are not inheriting to each other. Each class has a property in it that references to an instance of another class as below.
import java.util.ArrayList;
class Region {
private Directory areaDirectory;
public Region() {
areaDirectory = new Directory();
}
public Directory getAreaDirectory() {
return areaDirectory;
}
public void setAreaDirectory(Directory areaDirectory) {
this.areaDirectory = areaDirectory;
}
}
class Directory {
private ArrayList<Area> areaList;
public Directory() {
areaList = new ArrayList<>();
}
public ArrayList<Area> getAreaList() {
return areaList;
}
public void setAreaList(ArrayList<Area> areaList) {
this.areaList = areaList;
}
public Area addNewArea(){
Area area = new Area();
return area;
}
}
class Area {
private String Name;
public String getName() {
return Name;
}
public void setName(String name) {
Name = name;
}
public Region getAreaRegion() {
// This returns a new region but need the region it was created in
return new Region();
}
}
public class Scratch {
public static void main(String args[]) {
Region r = new Region();
Area a = r.getAreaDirectory().addNewArea();
a.setName("Demo");
//See getAreaRegion() method in Area class
System.out.println(a.getAreaRegion());
}
}
How to implement a method like getAreaRegion() such that it returns the region object r? How to setup inheritance in this example to get parent objects?
I have understood the business logic which you want to describe with codes as below:
There is a region. Every region has a directory. And every directory has an area.
In this case I think it would be nice if :
Region class holds reference to Directory field;
And Directory class also has reference for its own Region;
Directory class holds reference to Area field;
And Area class also has reference for its own Directory.
Then we can create classes in following way:
1.Region class
public class Region {
private Directory directory;
public Directory getDirectory() {
return directory;
}
public void setDirectory(Directory directory) {
this.directory = directory;
}
}
2.Directory class
class Directory{
private Region region;
private Area area;
public Region getRegion() {
return region;
}
public void setRegion(Region region) {
this.region = region;
}
public Area getArea() {
return area;
}
public void setArea(Area area) {
this.area = area;
}
}
3.Area class
class Area{
private Directory directory;
private String Name;
public Directory getDirectory() {
return directory;
}
public void setDirectory(Directory directory) {
this.directory = directory;
}
public String getName() {
return Name;
}
public void setName(String name) {
Name = name;
}
}
So we can get region of area as following:
area.getDirectory().getRegion();
I think this shows business logic better and simply. Hope it would be helpful for someone:)
I am currently creatin a TreeView where leaf elements should be checkable.
I created the sampleTreeView from the eclipse plugin that comes with a predefined Tree structure.
public class TreeObject {
private String name;
private TreeParent parent;
public TreeObject(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setParent(TreeParent parent) {
this.parent = parent;
}
public TreeParent getParent() {
return parent;
}
public String toString() {
return getName();
}
public Object getAdapter(Class<?> key) {
return null;
}
}
public class TreeParent extends TreeObject{
private ArrayList<TreeObject> children;
public TreeParent(String name) {
super(name);
children = new ArrayList<TreeObject>();
}
public void addChild(TreeObject child) {
children.add(child);
child.setParent(this);
}
public void removeChild(TreeObject child) {
children.remove(child);
child.setParent(null);
}
public TreeObject [] getChildren() {
return (TreeObject [])children.toArray(new TreeObject[children.size()]);
}
public boolean hasChildren() {
return children.size()>0;
}
}
I then found the following tutorial. He is using the TreeItem Object where it is easy to attach a Image. Can I somehow Copy this function or do I have to use the TreeItem object as my data structure?
The tutorial says at the beginning of part 2 that you should use a ContentProvider and LabelProvider for the TreeViewer rather than use TreeItem, and that is what you should do.
The getImage method of the label provider would return the checked / unchecked /null image.
When you need to change an image call TreeViewer.update or TreeViewer.refresh if the children of the object also need refreshing. This will call the label provider again.
I have been give a jar file to use that has a static inner class inside of another static inner class:
package externalJarFile;
public class Job
{
public static class GlobalVars
{
private List<Job.GlobalVars.Variable> variables;
public List<Job.GlobalVars.Variable> getVariable()
{
if (this.variables == null) {
this.variables = new ArrayList<Job.GlobalVars.Variable>();
}
return this.variables;
}
public static class Variable
{
String name;
String value;
public String getName() { return name; }
public void setName( String name ) { this.name = name; }
public String getValue() { return value; }
public void setValue( String value) { this.value= value; }
}
}
}
The problem I'm having is that I need to populate the "Job.GlobalVars" list, but I can't figure out how to reference the "Variables" type. Whenever I add:
import externalJarFile.Job.GlobalVars.Variable;
I get a compilation error that the type "externalJarFile.Job.GlobalVars.Variable" cannot be referenced. How can I create a new "Variable" instance to add to the "GlobalVars.getVariable()" list?
Here's a snippet that I tried (but didn't work):
Job.GlobalVars vars = new Job.GlobalVars();
Job.GlobalVars.Variable v = new Job.GlobalVars.Variable();
[Edited for clarity]
[UPDATE]
Ok, this is kinda weird. If I take the code from the original project and directly import it into mine, I'm able to reference the inner-inner-class. However, when I reference it when it's packaged inside of a jar file, it fails. MTK...
You forgot a space:
Job.GlobalVars vars = new Job.GlobalVars();
^
This works fine for me:
Job.GlobalVars.Variable var = new Job.GlobalVars.Variable();
var.setName("MByD");
Class job:
package mypackage;
import java.util.ArrayList;
import java.util.List;
public class Job {
public static class GlobalVars
{
private List<Variable> variables;
public List<Variable> getVariable()
{
if (this.variables == null) {
this.variables = new ArrayList<Variable>();
}
return this.variables;
}
public static class Variable
{
String name;
String value;
public String getName() { return name; }
public void setName( String name ) { this.name = name; }
public String getValue() { return value; }
public void setValue( String value) { this.value= value; }
}
}
}
Other class using GlobalVars and Variable. Import works very good.
package mypackage;
import mypackage.Job.GlobalVars;
import mypackage.Job.GlobalVars.Variable;
public class RunIt {
public static void main(String[] args) {
GlobalVars vars = new GlobalVars();
Variable v = new Variable();
}
}
No need to import anything. You should be able to just refer to your inner class by its name, "Variable", from the "Job" class:
private List<Variable> variables;
public List<Variable> getVariable()
They way you had stated above is correct. You should check to ensure that the jar file is in your classpath as that would definitely cause the import to fail and subsequently all future declarations.
import mypackage.Job.GlobalVars.Variable;
...
Variable v = new Variable();
I have a question concerning Json deserialization using Jackson.
I would like to deserialize a Json file using a class like this one:
(taken from http://wiki.fasterxml.com/JacksonInFiveMinutes)
public class User
{
public enum Gender { MALE, FEMALE };
public static class Name {
private String _first, _last;
public String getFirst() { return _first; }
public String getLast() { return _last; }
public void setFirst(String s) { _first = s; }
public void setLast(String s) { _last = s; }
}
private Gender _gender;
private Name _name;
private boolean _isVerified;
private byte[] _userImage;
public Name getName() { return _name; }
public boolean isVerified() { return _isVerified; }
public Gender getGender() { return _gender; }
public byte[] getUserImage() { return _userImage; }
public void setName(Name n) { _name = n; }
public void setVerified(boolean b) { _isVerified = b; }
public void setGender(Gender g) { _gender = g; }
public void setUserImage(byte[] b) { _userImage = b; }
}
A Json file can be deserialized using the so called "Full Data Binding" in this way:
ObjectMapper mapper = new ObjectMapper();
User user = mapper.readValue(new File("user.json"), User.class);
My problem is the usage of the inner class "Name". I would like to do the same thing without using inner classes. The "User" class would became like that:
import Name;
import Gender;
public class User
{
private Gender _gender;
private Name _name;
private boolean _isVerified;
private byte[] _userImage;
public Name getName() { return _name; }
public boolean isVerified() { return _isVerified; }
public Gender getGender() { return _gender; }
public byte[] getUserImage() { return _userImage; }
public void setName(Name n) { _name = n; }
public void setVerified(boolean b) { _isVerified = b; }
public void setGender(Gender g) { _gender = g; }
public void setUserImage(byte[] b) { _userImage = b; }
}
This means to find a way to specify to the mapper all the required classes in order to perform the deserialization.
Is this possible? I looked at the documentation but I cannot find any solution.
My need comes from the fact that I use the Javassist library to create such classes, and it does not support inner or anonymous classes.
Thank you in advance
There should be no difference between the static inner class Name, and the top-level class of the same name. The Jackson runtime should not be able to meaningfully distinguish between the two situations.
Have you tried moving the Name class out of User, changing it into a top-level class? It should still work as before.
edit: I just tried this, and it works fine when Name is a top-level class. The example had it as an inner class for the sake of brevity, I suspect.
mr. Skaffman's answer is right on. The only additional thing to mention is that unlike JAXB, Jackson does not generally require you to specify classes you operate on, except for the root class (and not always even that, if you use Polymorphic Handling).