title: Calculator clear result when pressing a new number
body: <p>I took help to create a calculator. For example 5+3=8.0, when I press a new number after the result is shown for example 3 it will just add to the old result like this, 8.3 instead of clearing and just typing 3 by itself. If I could get some help with this I would be very thankful
  I've been trying alot to fix it but I cant get it to work.</p>
  
  <p>/noob programmer</p>
  
  <pre><code>import java.awt.*;
  import javax.swing.*;
  import java.awt.event.*;
  
  public class Calculator extends JFrame implements ActionListener {
  
      JPanel[] row = new JPanel[5];
      JButton[] button = new JButton[19];
      String[] buttonString = {"7", "8", "9", "+",
                               "4", "5", "6", "-",
                               "1", "2", "3", "*",
                               ".", "/", "C", "√",
                               "+/-", "=", "0"};
      int[] dimW = {300,45,100,90};
      int[] dimH = {35, 40};
      Dimension displayDimension = new Dimension(dimW[0], dimH[0]);
      Dimension regularDimension = new Dimension(dimW[1], dimH[1]);
      Dimension rColumnDimension = new Dimension(dimW[2], dimH[1]);
      Dimension zeroButDimension = new Dimension(dimW[3], dimH[1]);
      boolean[] function = new boolean[4];
      double[] temporary = {0, 0};
      JTextArea display = new JTextArea(1,20);
      Font font = new Font("Times new Roman", Font.BOLD, 14);
  
      Calculator() {
          super("Calculator");
          setDesign();
          setSize(380, 250);
          setResizable(false);
          setDefaultCloseOperation(EXIT_ON_CLOSE);
          GridLayout grid = new GridLayout(5,5);
          setLayout(grid);
  
          for(int i = 0; i &lt; 4; i++)
              function[i] = false;
  
          FlowLayout f1 = new FlowLayout(FlowLayout.CENTER);
          FlowLayout f2 = new FlowLayout(FlowLayout.CENTER,1,1);
          for(int i = 0; i &lt; 5; i++)
              row[i] = new JPanel();
          row[0].setLayout(f1);
          for(int i = 1; i &lt; 5; i++)
              row[i].setLayout(f2);
  
          for(int i = 0; i &lt; 19; i++) {
              button[i] = new JButton();
              button[i].setText(buttonString[i]);
              button[i].setFont(font);
              button[i].addActionListener(this);
          }
  
          display.setFont(font);
          display.setEditable(false);
          display.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
          display.setPreferredSize(displayDimension);
          for(int i = 0; i &lt; 14; i++)
              button[i].setPreferredSize(regularDimension);
          for(int i = 14; i &lt; 18; i++)
              button[i].setPreferredSize(rColumnDimension);
          button[18].setPreferredSize(zeroButDimension);
  
          row[0].add(display);
          add(row[0]);
  
          for(int i = 0; i &lt; 4; i++)
              row[1].add(button[i]);
          row[1].add(button[14]);
          add(row[1]);
  
          for(int i = 4; i &lt; 8; i++)
              row[2].add(button[i]);
          row[2].add(button[15]);
          add(row[2]);
  
          for(int i = 8; i &lt; 12; i++)
              row[3].add(button[i]);
          row[3].add(button[16]);
          add(row[3]);
  
          row[4].add(button[18]);
          for(int i = 12; i &lt; 14; i++)
              row[4].add(button[i]);
          row[4].add(button[17]);
          add(row[4]);
  
          setVisible(true);
      }
  
      public void clear() {
          try {
              display.setText("");
              for(int i = 0; i &lt; 4; i++)
                  function[i] = false;
              for(int i = 0; i &lt; 2; i++)
                  temporary[i] = 0;
          } catch(NullPointerException e) {  
          }
      }
  
      public void getSqrt() {
          try {
              double value = Math.sqrt(Double.parseDouble(display.getText()));
              display.setText(Double.toString(value));
          } catch(NumberFormatException e) {
          }
      }
  
      public void getPosNeg() {
          try {
              double value = Double.parseDouble(display.getText());
              if(value != 0) {
                  value = value * (-1);
                  display.setText(Double.toString(value));
              }
              else {
              }
          } catch(NumberFormatException e) {
          }
      }
  
      public void getResult() {
          double result = 0;
          temporary[1] = Double.parseDouble(display.getText());
          String temp0 = Double.toString(temporary[0]);
          String temp1 = Double.toString(temporary[1]);
          try {
              if(temp0.contains("-")) {
                  String[] temp00 = temp0.split("-", 2);
                  temporary[0] = (Double.parseDouble(temp00[1]) * -1);
              }
              if(temp1.contains("-")) {
                  String[] temp11 = temp1.split("-", 2);
                  temporary[1] = (Double.parseDouble(temp11[1]) * -1);
              }
          } catch(ArrayIndexOutOfBoundsException e) {
          }
          try {
              if(function[2] == true)
                  result = temporary[0] * temporary[1];
              else if(function[3] == true)
                  result = temporary[0] / temporary[1];
              else if(function[0] == true)
                  result = temporary[0] + temporary[1];
              else if(function[1] == true)
                  result = temporary[0] - temporary[1];
              display.setText(Double.toString(result));
              for(int i = 0; i &lt; 4; i++)
                  function[i] = false;
          } catch(NumberFormatException e) {
          }
      }
  
      public final void setDesign() {
          try {
              UIManager.setLookAndFeel(
                      "com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
          } catch(Exception e) {   
          }
      }
  
      @Override
      public void actionPerformed(ActionEvent ae) {
          if(ae.getSource() == button[0])
              display.append("7");
          if(ae.getSource() == button[1])
              display.append("8");
          if(ae.getSource() == button[2])
              display.append("9");
          if(ae.getSource() == button[3]) {
              //add function[0]
              temporary[0] = Double.parseDouble(display.getText());
              function[0] = true;
              display.setText("");
          }
          if(ae.getSource() == button[4])
              display.append("4");
          if(ae.getSource() == button[5])
              display.append("5");
          if(ae.getSource() == button[6])
              display.append("6");
          if(ae.getSource() == button[7]) {
              //subtract function[1]
              temporary[0] = Double.parseDouble(display.getText());
              function[1] = true;
              display.setText("");
          }
          if(ae.getSource() == button[8])
              display.append("1");
          if(ae.getSource() == button[9])
              display.append("2");
          if(ae.getSource() == button[10])
              display.append("3");
          if(ae.getSource() == button[11]) {
              //multiply function[2]
              temporary[0] = Double.parseDouble(display.getText());
              function[2] = true;
              display.setText("");
          }
          if(ae.getSource() == button[12])
              display.append(".");
          if(ae.getSource() == button[13]) {
              //divide function[3]
              temporary[0] = Double.parseDouble(display.getText());
              function[3] = true;
              display.setText("");
          }
          if(ae.getSource() == button[14])
              clear();
          if(ae.getSource() == button[15])
              getSqrt();
          if(ae.getSource() == button[16])
              getPosNeg();
          if(ae.getSource() == button[17])
              getResult();
          if(ae.getSource() == button[18])
              display.append("0");
      }
  
      public static void main(String[] arguments) {
          Calculator c = new Calculator();
      }
  }
  </code></pre>