HI guys .
Stuck at this lesson .Someone help with an explanation of a calculator´s logic
in particular "IF" statement , just a little hint please
package com.practicaljava.lesson9;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JButton;
public class CalculatorEngine implements ActionListener {
Calculator parent; // a reference to the Calculator
// new variables
double storedNumber , enteredNumber ;
String selectedAction ;
// Constructor stores the reference to the
// Calculator window in the member variable parent
CalculatorEngine(Calculator parent){
this.parent = parent;
}
public void actionPerformed(ActionEvent e){
// Get the source of this action
JButton clickedButton = (JButton) e.getSource();
String dispFieldText = parent.getDisplayValue();
String clickedButtonLabel = clickedButton.getText();
if (!dispFieldText.equals("")){
if (clickedButton.getText() == ("+") || clickedButton.getText()
== ("-")|| clickedButton.getText() == ("*") ||
clickedButton.getText() == ("/")){
// Fetching figures from calculator and making it decimal
storedNumber = Double.parseDouble(parent.getDisplayValue());
selectedAction = clickedButton.getText();
// Clean a display
parent.setDisplayValue("");
}
else if ((clickedButton.getText() == ("="))
&& (selectedAction != null)) {
if (selectedAction==("+")) {
storedNumber = storedNumber+Double.parseDouble(parent.getDisplayV alue());
parent.setDisplayValue( "" + storedNumber);
}
}
}
// Get the button's label
else{
parent.setDisplayValue( dispFieldText +clickedButtonLabel);
}
}
}
Lesson 10
