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Okay, what happens if I create an object within a class, and when I make an instance of that class, I can only reference the object through the other object? Here's an example.

class SomeObject {
	int value = 99;
	}

class Test {
	SomeObject newObject = new SomeObject();
}


class game {
	public static void main(String[] arguments) {
	Test test1 = new Test();
	System.out.println(test1.newObject.value);
		
	}
}

Notice the "System.out.println" statement. I have to reference the "value" integer through "newObject," or else it doesn't work. If I just try to do newObject.value, it gives me an error. Why do I have to reference through that object and what did I just program here? Is there some kind of technique I just used that I unwillingly stumbles upon and is it an okay practice to initiate objects within classes? Thanks.

RO86 · Accepted Answer

OK if you want to know if this is good programming practice:

From my experience i will tell you some thing :

1- There is no problem to use object in side object

test1.newObject

2- you should not allow accessing variable from outside the class like this:

test1.newObject.value

because this violate OO concepts 'encapsulation' which means that you access the class object only by calling methods

How do you do that?

* Keep instance variables protected (with an access modifier, often private).

* Make public accessor methods, and force calling code to use those methods

rather than directly accessing the instance variable.

* For the methods, use the JavaBeans naming convention of

set<someProperty> and get<someProperty>.

E.M.Bed · Answer

This is best illustrated by example.

So now try the following:

class SomeObject {
int value = 99;
}

class Test {
SomeObject newObject = new SomeObject();
}

class game {
public static void main(String[] arguments) {
Test test1 = new Test();
Test test2 = new Test();
System.out.println( test1.newObject.value);
System.out.println( test2.newObject.value);
}
}

Now we've got 2 instances of Test each with their own separate instance of SomeObject. We have to access the internal value separately to distinguish them.

Now this will make things clearer hopefully:

class SomeObject {
  int value=0; //default
  SomeObject (int val) { // constructor
    this.value = val;
  }
}

class Test {
  SomeObject newObject;
  Test (int val) { // constructor
    this.newObject = new SomeObject(val);
  }
}

public class game {
public static void main(String[] arguments) {
Test test1 = new Test(16);
Test test2 = new Test(23);
System.out.println( test1.newObject.value);
System.out.println( test2.newObject.value);
}
}

Output is 
16
23

We have added constructors for both Test and SomeObject to initialise the value variable. You can see from the output that there is a different instance of SomeObject in Test1 and Test2 which is why you need to explicitly reference the object you require to avoid ambiguity.. 

If you just did this:

class SomeObject {
int value = 99;
}

public class game {
public static void main(String[] arguments) {
SomeObject newObject = new SomeObject();
System.out.println( newObject.value);
}
}

There is only a single instance of SomeObject contained within the game class so can be referenced directly within the game class as opposed to another class.

Note game should be public in a file game.java.

hairy · Answer

make value a static variable....(note all objects refer to same value now).......
it can b now accessed Test.value=123;

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