Develop Reference

How Do I Import Classes From Another Package and Folder in Java?

I just started studying OOP and Packages in Java. I have a question regarding package importing in Java.
I have two files, named ImportThis.java and Here.java
The directory for ImportThis.java on my local machine is F:\VS Codes\master\folderone\folderoneone\ImportThis.java. And the contents of ImportThis.java is:
package master.folderone.folderoneone;
public class ImportThis {
public static void aStaticMethod() {
System.out.println("Hello World");
}
}
The directory for Here.java on my local machine is F:\VS Codes\master\foldertwo\foldertwotwo\Here.java. And the contents of Here.java is:
package master.foldertwo.foldertwotwo;
public class Here {
public static void anotherMethod() {
ImportThis.aStaticMethod();
}
}
By looking at the contents of Here.java, you might be able to tell that I want to import the class ImportThis from ImportThis.java to Here.java, and it is indeed what I've been trying to do. But both ImportThis.java and Here.java came from different folders and packages. I've tried using import master.folderone.folderoneone.ImportThis; on Here.java but VS Code says it cannot be resolved. Looking forward to the answer for my question!
EDIT: Changed package names and lowercased the folder names

Try:
package master.foldertwo.foldertwotwo;
import master.folderone.folderoneone.ImportThis; //<-import statement
public class Here {
public static void anotherMethod() {
ImportThis.aStaticMethod();
}
}

How Default package is created and where?

In this How Default Package is Created where class file is stored
class Package
{
public static void main(String[] args) {
System.out.println("Default Package");
}
}

When we create a java class and dodnot mention any package name for creating this particular class within any java/web project the eclipse /netbeans will automatically creates the default package.

Netbeans doesnt recognize class in the same package

i am creating a little game with libgdx framework and netbeans 8. I have all java classes in a single package that match with the directory structure.
The problem is that i cant import or isntantiate classes, for example:
package com.myfolder.folder2;
import ...
public class myclass1{
private myclass2 mc2;
etc...
}
In this case myclass2 is public and is inside the package but netbeans complains "cannot find symbol".
If i try with alt+enter, netbeans says "Create class myclass2 in package com.myfolder.folder2" or the same like an inner class. If i press the first option, netbeans create a class in the package with the file name myclass2_1 (becouse myclass2 exists!), and myclass1 doesnt recognize the new class.
If i try to import the class:
import com.myfolder.folder2.myclass2;
It gives me the same error, and in fact the code completion tool only gives me one crazy option in the import sentence:
import com.myfolder.folder2.myclass1;
Import the same class.
What can i do? I never have these problems using netbeans.
PD: Sorry for my english :)

You can use a class inside the same package like this:
ClassName classVariableName = new ClassName();
Then when you want to run something from the class you would put
classVariableName.MethodThatIWantToRun();
Or if you want to access a property from that method you would access it in a very similar way:
classVarabileName.PropertyIWantToAccess
Example:
You have one class with a property you want to access:
class MyClass {
public int MyProperty = 5;
}
You access it in this class:
public class MainClass {
public static void main(String[] args) {
MyClass myClass = new MyClass();
System.out.println(myClass.MyProperty);
}
}
If that doesn't work than you might have some other problem.

It was an error with one of my class package definition:
public class DesktopLauncher{
public static void main(String... args){
LwjglApplicationConfiguration cfg = new LwjglApplicationConfiguration();
.
.
.
new LwjglApplication(new MyClass, config);
}
}
It was in MyClass, becouse i copied a snippet from an older project, and accidentally copied the older package.

NetBeans is not smart enough,
Solution: just declare the package name in all classes, example:
Class A:
package test;
public class ClassA {
public static void main(String[ ] args) {
ClassB.myFunctionB();
}
}
Class B:
package test;
public class ClassB {
public static void myFunctionB () {
System.out.print("I am ClassB!");
}
}

Getting Netbeans Java program to compile

I'm new to java, and I've been trying to get my program to compile using Netbeans. HelloWorldApp.java uses the Greeter class in Greeter.java. I keep getting errors and I can't figure it out. I understand that you have to include "packages" or something. I don't have a lot of experience with Netbeans either. But I would love for this to work.
Here is the HelloWorldApp.java:
package helloworldapp;
import Greeter
public class HelloWorldApp
{
public static void main(String[] args)
{
Greeter myGreeterObject = new Greeter();
myGreeterObject.sayHello();
}
}
And here is Greeter.java:
public class Greeter
{
public void sayHello()
{
System.out.println("Hello, World!");
}
}

Change the first line of Greeter to
package helloworldapp;
And then remove
import Greeter
from HelloWorldApp. You only need to import classes that are in other packages. Also, an import line is terminated with a semicolon. Finally, import is always optional and a convenience for the developer; as an example,
import java.util.Calendar;
Allows you to write
Calendar cal = Calendar.getInstance();
But, without the import you could still use
java.util.Calendar cal = java.util.Calendar.getInstance();

Just put the Greeter class in the same folder (i.e. package) as the other file and remove the "import Greeter" statement. You should put every class in a package as you did with the HelloWorldApp class.
If you leave classes without package (i.e. in the root folder) you cannot import them.

As long as both are in the same package (folder) there will be no need for the "import Greeter" statement, this should fix it, hope this helps!

Is it possible to import class file with default package?

I have created a project and Hello.java file without package name
public class Hello {
public String sayHello(){
return "Say Hello";
}
}
I exported this project into hello.jar.
Now I have created another project and Main.java to call sayHello() method. I added hello.jar in classpath but the below code showing me an error 'Hello cannot be resolved to a type'
public class Main {
public static void main(String[] args){
Hello h=new Hello(); // Error
}
}

It's not possible due to the fact that your Hello.java class needs to be inside a package stored in your JAR file to enable you to reference it. The structure of your JAR should at least be
hello.jar/packageName/Hello.java
after creating it like that it will be imported as
import packageName;
and you will be able to use classes from aformentioned package.

No. It is not possible.
Try giving package name to Hello java file and then create again jar and then write import statement in Main class file
package com;
public class Hello {
public String sayHello(){
return "Say Hello";
}
}
and in Main class add following line
import com.Hello;
public class Main {
public static void main(String[] args){
Hello h=new Hello();
}
}