JCalc.java

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


public class JCalc{

        public static void main(String[] args){
          JFrame f = new CalculatorFrame("JCalculator");
          f.setSize(375,275);
          f.setVisible(true);   
        }
}
        //Frame Class
        class CalculatorFrame extends JFrame{

          private JTextField tf = new JTextField("0",28);
          private String previousNumber = "0";
          private String currentNumber = "0";
          private char lastOperator = 0;
          private boolean equalsHit = false;
          private boolean waiting = false;
      
          public CalculatorFrame(String title){
            super(title);
            Container contentPane = getContentPane();//get the context in which objects will be placed
            contentPane.setLayout(new BorderLayout());//sets LayoutManger of context

            //Top Panel
            JPanel textField = new JPanel(new FlowLayout(FlowLayout.RIGHT));//Begin textField (top) Panel
            tf.setHorizontalAlignment(JTextField.RIGHT);
            tf.setEditable(false);
            textField.add(tf);//end textField Panel
            contentPane.add(textField, BorderLayout.NORTH);//add top Panel
            OperationListener ol = new OperationListener();
            //Buttons
            JButton divide = new JButton("/");
            divide.addActionListener(ol);
            JButton square = new JButton("x^2");
            square.addActionListener(ol);
            JButton multiply = new JButton("*");
            multiply.addActionListener(ol);
            JButton exponentiate = new JButton("X^Y");
            exponentiate.addActionListener(ol);
            JButton subtract = new JButton("-");
            subtract.addActionListener(ol);
            JButton mod = new JButton("%");
            mod.addActionListener(ol);
            NumberListener nl = new NumberListener();
            JButton decimal = new JButton(".");
            decimal.addActionListener(nl);
            JButton equals = new JButton("=");
            equals.addActionListener(ol);
            JButton add = new JButton("+");
            add.addActionListener(ol);
            JButton factorial = new JButton("!");
            factorial.addActionListener(ol);
            //End generation of Buttons
            
            //Center Panel
            JPanel buttonField = new JPanel(new GridLayout(4,5,3,3));//Creates buttonField Panel 
            for(int i = 7; i <= 9; i++){//Begin placement of Buttons in CENTER Panel
              JButton temp = new JButton(i + "");;
              temp.addActionListener(nl);
              buttonField.add(temp);
            }//end for
            buttonField.add(divide);
            buttonField.add(square);
            for(int i = 4; i <= 6; i++){
              JButton temp = new JButton(i + "");
              temp.addActionListener(nl);
              buttonField.add(temp);
            }//end for
            buttonField.add(multiply);
            buttonField.add(exponentiate);
            for(int i = 1; i <= 3; i++){
              JButton temp = new JButton(i + "");
              temp.addActionListener(nl);
              buttonField.add(temp);
            }//end for
            buttonField.add(subtract);
            buttonField.add(mod);
            JButton zero = new JButton("0");
            zero.addActionListener(nl);
            buttonField.add(zero);
            buttonField.add(decimal);
            buttonField.add(equals);
            buttonField.add(add);
            buttonField.add(factorial);
            contentPane.add(buttonField,BorderLayout.CENTER);//End Placement of Buttons in CENTER Panel
             
            //Start Bottom Panel
            JPanel control = new JPanel(new GridLayout(1,2,3,3));
            JButton clear = new JButton("Clear");
            clear.addActionListener(new FunctionListener());
            control.add(clear);
            contentPane.add(control, BorderLayout.SOUTH);
            //End Bottom Panel
            addWindowListener(new WindowCloser());//activates close button
        }//end CalculatorFrame

        class WindowCloser extends WindowAdapter{ //Closes Window
          public void windowClosing(WindowEvent evt){
            System.exit(0);
          }//end windowClosing
        }//end WindowCloser
    

        class NumberListener implements ActionListener{
          public void actionPerformed(ActionEvent evt){
              String userInput = evt.getActionCommand();
              String currentDisplay = tf.getText();
              if(!userInput.equals(".")){
                if(equalsHit){
                  String output = userInput;
                  equalsHit = false;
                  waiting = false;
                  tf.setText(output);
                }//end if
                else if(waiting){
                  String output = userInput;
                  tf.setText(output);
                  waiting = false;
                }//end if
                else if(currentDisplay.equals("0"))
                  tf.setText(userInput);
                else
                  tf.setText(currentDisplay + userInput);
              }//end if
              else{
                if(equalsHit){
                  equalsHit = false;
                  waiting = false;
                  tf.setText("0.");
                }//end if
                else if(waiting){
                  waiting = false;
                  tf.setText("0.");
                }//end if
                else if(currentDisplay.equals("0"))
                  tf.setText(currentDisplay + ".");
                else if(currentDisplay.indexOf(".") < 0)
                  tf.setText(currentDisplay + ".");
              }//end else
          }//end actionPerformed
        }//end NumberListener

        class FunctionListener implements ActionListener{
          public void actionPerformed(ActionEvent evt){
            String userInput = evt.getActionCommand();
            if(userInput.equals("Clear"))
              clear();
          }//end actionPerformed

          public void clear(){
              previousNumber = "0";
              currentNumber = "0";
              lastOperator = 0;
              equalsHit = false;
              waiting = false;
              tf.setText("0");
            }//end clear
          }//end FunctionListener


        class OperationListener implements ActionListener{
          public void actionPerformed(ActionEvent evt){
            String userInput = evt.getActionCommand();
            char character = userInput.charAt(0);
            switch(character){
              case '-': subtract();
                        break;
              case '*': multiply();
                        break;
              case '/': divide();
                        break;
              case '+': add();
                        break;
              case '=': equalsSign();
                        break;
              case 'x': square();
                        break;
              case 'X': exponentiate();
                        break;
              case '!': factorial();
                        break;
              case '%': mod();
                        break;
            }
          }

          public void subtract(){
            if(!waiting){
              equalsHit = false;
              waiting = true;
              previousNumber = tf.getText();
              lastOperator = '-';
            }
            else if(lastOperator == '-'){
              String currentNumber = tf.getText();
              double num1 = 0; double num2 = 0;
              try{
                num1 = Double.parseDouble(previousNumber);
                num2 = Double.parseDouble(currentNumber);
              }
              catch(NumberFormatException e){
                tf.setText("Error!!! Invalid Number");
                previousNumber = "0";
                lastOperator = 0;
                equalsHit = true;
              }
              double numericAnswer = num1 - num2;
              previousNumber = numericAnswer + "";
              previousNumber = format(previousNumber);
              tf.setText(previousNumber);
            }
          }

          public void multiply(){
            if(!waiting){
              equalsHit = false;
              waiting = true;
              previousNumber = tf.getText();
              lastOperator = '*';
            }
            else if(lastOperator == '*'){
              String currentNumber = tf.getText();
              double num1 = 0; double num2 = 0;
              try{
                num1 = Double.parseDouble(previousNumber);
                num2 = Double.parseDouble(currentNumber);
              }
              catch(NumberFormatException e){
                tf.setText("Error!!! Invalid Number");
                previousNumber = "0";
                lastOperator = 0;
                equalsHit = true;
              }
              double numericAnswer = num1 * num2;
              previousNumber = numericAnswer + "";
              previousNumber = format(previousNumber);
              tf.setText(previousNumber);
            }
          }

          public void divide(){
            if(!waiting){
              equalsHit = false;
              waiting = true;
              previousNumber = tf.getText();
              lastOperator = '/';
            }
            else if(lastOperator == '/'){
              String currentNumber = tf.getText();
              double num1 = 0; double num2 = 0;
              try{
                num1 = Double.parseDouble(previousNumber);
                num2 = Double.parseDouble(currentNumber);
              }
              catch(NumberFormatException e){
                tf.setText("Error!!! Invalid Number");
                previousNumber = "0";
                lastOperator = 0;
                equalsHit = true;
              }
              double numericAnswer = num1 / num2;
              previousNumber = numericAnswer + "";
              previousNumber = format(previousNumber);
              tf.setText(previousNumber);
            }
          }

          public void add(){
            if(!waiting){
              equalsHit = false;
              waiting = true;
              previousNumber = tf.getText();
              lastOperator = '+';
            }
            else if(lastOperator == '+'){
              String currentNumber = tf.getText();
              double num1 = 0; double num2 = 0;
              try{
                num1 = Double.parseDouble(previousNumber);
                num2 = Double.parseDouble(currentNumber);
              }
              catch(NumberFormatException e){
                tf.setText("Error!!! Invalid Number");
                previousNumber = "0";
                lastOperator = 0;
                equalsHit = true;
              }
              double numericAnswer = num1 + num2;
              previousNumber = numericAnswer + "";
              previousNumber = format(previousNumber);
              tf.setText(previousNumber);
            }
          }

          public void equalsSign(){
          if(!equalsHit){
            currentNumber = tf.getText();
          }
            equalsHit = true;
            double num1 = 0; double num2 = 0;
            try{
              num1 = Double.parseDouble(previousNumber);
              num2 = Double.parseDouble(currentNumber);
            }
            catch(NumberFormatException e){
              tf.setText("Error!!! Invalid Number");
              previousNumber = "0";
              lastOperator = 0;
              equalsHit = true;
            }
            switch(lastOperator){
              case '*':  previousNumber = (num1 * num2) + "";
                         break;
              case '+':  previousNumber = (num1 + num2) + "";
                         break;
              case '-':  previousNumber = (num1 - num2) + "";
                         break;
              case '/':  previousNumber = (num1 / num2) + "";
                         break;
              case 'X':  previousNumber = Math.pow(num1,num2) + "";
                         break;
              case '%':  previousNumber = (num1 % num2) + "";
                         break;
            }
            previousNumber = format(previousNumber);
            tf.setText(previousNumber);
          }

          public void square(){
            previousNumber = tf.getText();
            double number = 0;
            try{
              number = Double.parseDouble(previousNumber);
            }
            catch(NumberFormatException e){
             tf.setText("Error!!! Invalid Number");
             previousNumber = "0";
             lastOperator = 0;
             equalsHit = true;
            }
            number *= number;
            previousNumber = number + "";
            previousNumber = format(previousNumber);
            tf.setText(previousNumber);
            equalsHit = true;
            lastOperator = 'x';
          }

          public void exponentiate(){
            if(!waiting){
              equalsHit = false;
              waiting = true;
              previousNumber = tf.getText();
              lastOperator = 'X';
            }
            else if(lastOperator == 'X'){
              String currentNumber = tf.getText();
              double num1 = 0; double num2 = 0;
              try{
                num1 = Double.parseDouble(previousNumber);
                num2 = Double.parseDouble(currentNumber);
              }
              catch(NumberFormatException e){
                tf.setText("Error!!! Invalid Number");
                previousNumber = "0";
                lastOperator = 0;
                equalsHit = true;
              }
              double numericAnswer = Math.pow(num1,num2);
              previousNumber = numericAnswer + "";
              previousNumber = format(previousNumber);
              tf.setText(previousNumber);
            }
          }

          public void factorial(){
            previousNumber = tf.getText();
            double number = 0;
            try{
              number = Double.parseDouble(previousNumber);
            }
            catch(NumberFormatException e){
             tf.setText("Error!!! Invalid Number"); 
             previousNumber = "0";
             lastOperator = 0;
             equalsHit = true;
            }
            int factorial = (int) number;
            if(factorial == 0){
              factorial = 1;
              previousNumber = factorial + "";
              tf.setText(previousNumber);
              equalsHit = true;
              lastOperator = 'x';
            }
            else{
              for(int i = (int) number - 1; i > 1; i--){
                factorial *= i;
              }
              previousNumber = factorial + "";
              tf.setText(previousNumber);
              equalsHit = true;
              lastOperator = 'x';
            }
          }

          public void mod(){
            if(!waiting){
              equalsHit = false;
              waiting = true;
              previousNumber = tf.getText();
              lastOperator = '%';
            }
            else if(lastOperator == '%'){
            if(!equalsHit){
              currentNumber = tf.getText();
            }
              System.out.println(currentNumber);
              double num1 = 0; double num2 = 0;
              try{
                num1 = Double.parseDouble(previousNumber);
                num2 = Double.parseDouble(currentNumber);
              }
              catch(NumberFormatException e){
                tf.setText("Error!!! Invalid Number");
                previousNumber = "0";
                lastOperator = 0;
                equalsHit = true;
              }
              double numericAnswer = num1 % num2;
              previousNumber = numericAnswer + "";
              previousNumber = format(previousNumber);
              tf.setText(previousNumber);
            }
          }

          public String format(String answer){
            double theAnswer = 0;
            try{
              theAnswer = Double.parseDouble(answer);
            }
            catch(NumberFormatException e){
                tf.setText("Error!!! Invalid Number");
                previousNumber = "0";
                lastOperator = 0;
                equalsHit = true;
            }
            if(theAnswer == (int) theAnswer)
              return (int) theAnswer + "";
            else
              return answer;
          }
     }
}

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