how to use a class in the java file containing multiple classes

Question

For example,

//Package1/File1.java
class A{
...
}

public class File1{
...
}

How can I use the class A in the different File2.java? And what's the package that A is belong to? Package1 or default? Thank you!

Try to google it, there are more than alot explanations across the internet. — Maksym, Nov 23 '14 at 10:58

score 0 · Answer 1 · edited May 23 '17 at 12:12

It's simple. Create an instance of the class File1 inside the main method of File2.java and do all your work there.

//package1/File2.java

public class File2
{
    ...
}

public File2()  //constructor
{

}

//Main method
public static void main(String[] args)
{
    File1 f1 = new File1();
    //do your rest of the work here
}

You can't use the class A in File2.java because it's not public, and you can't have more than one public class in a .java file.

In order to access class A inside File2.java, you have to create another java class named A in another java file named A.java, and then make this A class public, and create instance of A inside File2.java.

Inside A.java:

 //package1/A.java
 public class A{
    ...
 }

 public A() //constructor
 {
     ...
 }

Now in File2.java :

 //package1/File2.java 
 public class File2()
 {
     ...
 }

 public static void main(String[] args)
 {
     A objA = new A();
     //do your rest of the work here
 }

Go through the following link for a better understanding: Why can't two public classes be defined in one file in java?

score 0 · Answer 2 · answered Nov 23 '14 at 11:02

Both the file belong to same package that package1/file1.java. See understand like this : A class like file1.java can have many sub classes as "class A" but the public class can only be that class which has same name as file (file1.java) class. I think I make some sense here.

how to use a class in the java file containing multiple classes

2 Answers2