How to get Variables values from other class in java to 2 different class

January 27, 2022

i want to ask about Object Oriented Programming stuff.

so i got 3 classes, ( Main Class, Second Class, Third Class ) on same Package.

Main.class

public static void main(String[] args) {
    int var_main = 0;
    Scanner input = new Scanner(System.in);
    Second second = new Second();
    System.out.print("Input some number to save : ");
    var_main = input.nextInt();
    second.setCount(var_main);
    new Third();
}

Second.class

public class Second {
private int count;
public void setCount(int count) {
    this.count = count;
}
public int getCount() {
    return this.count;
}

}

Third Class

public class Third {
public Third() {
    Second second = new Second();
    System.out.println("Number Saved from Main Class : "+second.getCount());
}

}

The output from the Third.class is 0 why it’s not values from the Main class ? i still confused with this, thank you very much.

>Solution :

As others mentioned in the comment, you are creating the brand new Second object inside the Third class constructor.

I modified your code and added the comments so you can understand what others commented on your question.

Main

public static void main(String[] args) {
    int var_main = 0;
    Scanner input = new Scanner(System.in);
    Second second = new Second();
    System.out.print("Input some number to save : ");
    var_main = input.nextInt();
    second.setCount(var_main);
    //pass the second object which you updated the count in order to print the count inside Third Constructor. 
    new Third(second);
}

Second class

public class Second {
private int count;
public void setCount(int count) {
    this.count = count;
}
public int getCount() {
    return this.count;
}

}

Third Class

public class Third {
public Third(Second second) { //Now you need to pass the second reference to this Third class constructor to print the result you expecting..
    
    // You are creating new Second object and whatever you set the count in main class is different and this one is different..  
    //Second second = new Second();
    System.out.println("Number Saved from Main Class : "+second.getCount());
}
}