[itsmichelle]

This is a very primative code of a java swing calculator. I have assigned all the number buttons and the operator buttons and I can add, subtract, multiply, and divide two numbers together. However, my teacher wants the operators to follow the algebraic order of operations by chaining multiple operations. Such as, 7 + 4 * 2= 15. The operatorListener is the ActionListener for the operator buttons. Thanks for any help you can give me.

import java.awt.*;
import javax.swing.*;
import java.lang.*;
import java.awt.event.*;
import java.util.*;

import javax.swing.event.*;

public class Calculator extends JFrame {
	
	JTextField textField;
	private boolean startNumber= true;
	private int resultTotal;
	private String operator= "=";
	
	public static void main(String[] args) {
		Calculator calc = new Calculator();
		calc.setVisible(true);
	}
	
	public Calculator() {
		setTitle("Calculator");
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setSize(300,400);
		setLayout(new BorderLayout());
		
		JPanel textPanel= new JPanel();
		textPanel.setLayout(new FlowLayout());
		textField= new JTextField("0", 20);
		textField.setHorizontalAlignment(JTextField.RIGHT);
		textField.setBackground(Color.WHITE);
		textPanel.add(textField);
		add(textPanel, BorderLayout.NORTH);
		
		JPanel arithmeticFunctions= new JPanel();
		arithmeticFunctions.setBackground(Color.WHITE);
		arithmeticFunctions.setLayout(new GridLayout(5,1));
		
		JButton divideButton= new JButton("/");
		divideButton.addActionListener(new operatorListener());
		arithmeticFunctions.add(divideButton);
		JButton multiplyButton= new JButton("x");
		multiplyButton.addActionListener(new operatorListener());
		arithmeticFunctions.add(multiplyButton);
		JButton subtractButton= new JButton("-");
		subtractButton.addActionListener(new operatorListener());
		arithmeticFunctions.add(subtractButton);		
		JButton addButton= new JButton("+");
		addButton.addActionListener(new operatorListener());
		arithmeticFunctions.add(addButton);
		JButton equalButton= new JButton("=");
		equalButton.addActionListener(new operatorListener());
		arithmeticFunctions.add(equalButton);
		add(arithmeticFunctions, BorderLayout.EAST);
		
		JPanel numberPad= new JPanel();
		numberPad.setBackground(Color.WHITE);
		numberPad.setLayout(new GridLayout(4,3));
		
		JButton seven= new JButton("7");
		seven.addActionListener(new numberListener());
		numberPad.add(seven);
		JButton eight= new JButton("8");
		eight.addActionListener(new numberListener());
		numberPad.add(eight);
		JButton nine= new JButton("9");
		nine.addActionListener(new numberListener());
		numberPad.add(nine);
		JButton four= new JButton("4");
		four.addActionListener(new numberListener());
		numberPad.add(four);
		JButton five= new JButton("5");
		five.addActionListener(new numberListener());
		numberPad.add(five);
		JButton six= new JButton("6");
		six.addActionListener(new numberListener());
		numberPad.add(six);
		JButton one= new JButton("1");
		one.addActionListener(new numberListener());
		numberPad.add(one);
		JButton two= new JButton("2");
		two.addActionListener(new numberListener());
		numberPad.add(two);
		JButton three= new JButton("3");
		three.addActionListener(new numberListener());
		numberPad.add(three);
		JButton zero= new JButton("0");
		zero.addActionListener(new numberListener());
		numberPad.add(zero);
		JButton decimal= new JButton(".");
		decimal.addActionListener(new numberListener());
		numberPad.add(decimal);
		JButton posNeg= new JButton("+/=");
		numberPad.add(posNeg);
		add(numberPad, BorderLayout.WEST);
		
		
		JPanel cent= new JPanel();
		cent.setBackground(Color.WHITE);
		cent.setLayout(new FlowLayout());
		
		JButton c= new JButton("C");
		cent.add(c);
		add(cent, BorderLayout.CENTER);
	}
	
	private void actionClear() {
		startNumber= true;
		textField.setText("0");
		resultTotal=0;
		operator= "=";
	}

	public class numberListener implements ActionListener {
		public void actionPerformed(ActionEvent e) {
			String number= e.getActionCommand();
			if (startNumber) {
				textField.setText(number);
				startNumber= false;
			}
			else {
				textField.setText(textField.getText()+ number);
			}   
		}
	}
	
	public class operatorListener implements ActionListener {
		public void actionPerformed(ActionEvent e) {
			
			if (startNumber)
				actionClear();
			else
				startNumber= true;
		   
			try {
				String numOperator= textField.getText();
				int currentTotal= Integer.parseInt(numOperator);

				if (operator.equals("/")) {
					resultTotal /= currentTotal;
				}
				else if (operator.equals("x")) {
					resultTotal *= currentTotal;
				}
				else if (operator.equals("-")) {
					resultTotal -= currentTotal;
				}
				else if (operator.equals("+")) {
					resultTotal += currentTotal;
				}
				
					if (operator.equals("=")) {
					resultTotal= currentTotal;
				}
				textField.setText("" + resultTotal);
			}
			   
				
			
			catch (NumberFormatException ex) {
				actionClear();
			}
			
			operator= e.getActionCommand();
		   
		}
	}
	
	
}