core java

[Korada Rajshekar]

If we have a instance variable like int i=10 and for that class we have two objects if we change the value of i using first object then how can it notify to second object that the value of 'i' is changed....Without using Threads concept....just using normal objects

[Seetharaman Venkatasamy]

introduce a method which takes the same object as an argument. now test the argument object's instance field and perform a operation..something like below:

class TestObject
{
public boolean isValueChanged(TestObject e)
{
	if(e.i != 10)
	{
		return true;
	}
	return false;
}
}
now, TestObject obj = new TestObject();
obj.isValueChanged(new TestObject());

[Seetharaman Venkatasamy]

Please, UseAMeaningfulSubjectLine .

[Rob Spoor]

I'd probably add support for PropertyChangeListener, through PropertyChangeSupport:

class MyObject
{
    private int i;
    private String s;
    private PropertyChangeSupport pcs = new PropertyChangeSupport(this);

    // getters

    // setters
    public void setI(int i)
    {
        if (i != this.i)
        {
            int oldI = this.i;
            this.i = i;
            pcs.firePropertyChange("i", oldI, i);
        }
    }

    public void setS(int s)
    {
        if ((s == null ? this.s != null : !s.equals(this.s))) // or !Objects.equals(s, this.s) in Java 7
        {
            String oldS = this.s;
            this.s = s;
            pcs.firePropertyChange("s", oldS, s);
        }
    }

    // property change listener support
    public void addPropertyChangeListener(String propertyName, PropertyChangeListener l)
    {
        pcs.addPropertyChangeListener(propertyName, l);
    }

    public void removePropertyChangeListener(String propertyName, PropertyChangeListener l)
    {
        pcs.removePropertyChangeListener(propertyName, l);
    }
}

MyObject object = new MyObject();
object.addPropertyChangeListener("i", ...);