In Calculator class , two methods :

public void setDisplayValue(String val){
displayField.setText(val);
}

public String getDisplayValue() {
return displayField.getText();
}

where written out of a class's constructor .
Please, can someone explain why ?

Java methods are inherited, constructors ARE NOT!

So, following the instructions in Lesson 9 I changed my CalculatorEngine to look like the following:

public class CalculatorEngine implements ActionListener
{
Calculator parent; // a reference to the Calculator

// Constructor stores the reference to the Calculator
// window in the member variable parent
CalculatorEngine(Calculator parent)
{
this.parent = parent;
}
...

But that in turn resulted in this:

// Add action listener
CalculatorEngine calcEngine = new CalculatorEngine();
button0.addActionListener(calcEngine);
...

CalculatorEngine now requires a value be passed to it. Can someone tell me what gets passed to this class now, I'm new and a bit confused.

Thanks.

Hi could you try this out

CalculatorEngine calcEngine = new CalculatorEngine(this);