How to change an instance variable that contains a changed instance variable

Question

How come setWav doesn't change the wav in wav + " " + "Grapes"? Do I have to create a set method for add if I want it to output Oranges? Grapes?

EDIT: Thanks everyone for the help, much appreciated.

package javaapplication1;

public class JavaApplication1 {

    public static void main(String[] args) 
    {
        NewClass object1 = new NewClass();
        System.out.println(object1.getAdd());
        object1.setWav("Oranges?");
        System.out.println(object1.getAdd());    


    }
}

OUTPUT:

Burgers Grapes

Burgers Grapes

package javaapplication1;

public class NewClass 
{
    private String wav;
    private String add;

    public NewClass()
    {
        wav = "Burgers";
        add = wav + " " + "Grapes";       

    }

    public void setWav(String wav)
    {
        this.wav = wav;        
    }
    public String getWav()
    {
        return wav;
    }

    public String getAdd()
    {
        return add;
    }    

}

arshajii · Accepted Answer · 2012-09-18 22:36:15Z

2

Your getAdd method returns add. You set the value of add in the NewClass constructor but nowhere else, hence it remains unchanged even when you change wav (these two variables are not related in any way, changing one will not effect the other). You can try this:

public void setWav(String wav) {
    this.wav = wav;  
    add = wav + " " + "Grapes";  // i.e. add = wav + " Grapes";
}

answered Sep 18, 2012 at 22:36

arshajii

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Comments

zeller · Accepted Answer · 2012-09-18 22:36:13Z

2

You don't refresh add when you call setWav. Copy this line from the ctor to the setter:

add = wav + " " + "Grapes";

And it will work.

answered Sep 18, 2012 at 22:36

zeller

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Comments

jonathan · Accepted Answer · 2012-09-18 22:38:55Z

2

In your example the constructor is responsible for updating "add". But the problem is that its only invoked once, which is when the class is instantiated.

It happens on this line: NewClass object1 = new NewClass();

You could change setWav into this:

public void setWav(String wav)
{
    this.wav = wav;
    this.add = wav + " " + "Grapes";
}

This way it would update add every time setWav is called.

answered Sep 18, 2012 at 22:38

jonathan

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