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Java - enter multiple values into array via a single textfield [closed]

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With this code, i want to develop a program that enables the user to enter 5 int values into a single textfield. These values will be stored in an array and upon pressing the button, a bar graph will be drawn to represent the entered values. Class BtnHandler handles the button click event and class gegHandler handles the textfield enter event. I can't get the user input to be collected in the array. Here is my code.
package voorbeeld0805;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Vb0805 extends JFrame {
public static void main( String args[] ) {
JFrame frame = new Vb0805();
frame.setSize( 300, 300 );
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
frame.setTitle( "Voorbeeld 0805" );
frame.setContentPane( new Tekenpaneel() );
frame.setVisible( true );
}
}
class Tekenpaneel extends JPanel {
private Staafdiagram staafdiagram;
private JButton knopTeken;
private JTextField gegevensVak;
private JLabel lblNo;
private int[] lengtes = new int [5];
public Tekenpaneel() {
setBackground( Color.ORANGE );
knopTeken = new JButton("Teken");
knopTeken.addActionListener(new BtnHandler());
gegevensVak = new JTextField(5);
gegevensVak.addActionListener(new gegHandler());
lblNo = new JLabel("Enter Value");
add(knopTeken);
add (gegevensVak);
add (lblNo);
}
public void paintComponent( Graphics g ) {
super.paintComponent( g );
if (staafdiagram != null)
{
staafdiagram.teken( g, 50, 250 );
}
this.requestFocusInWindow();
}
class BtnHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
//To test using the first constructor. Works perfectly
/*int [] lengtes = { 144, 98, 117, 130, 172, 173 };
staafdiagram = new Staafdiagram( lengtes, 30 );*/
repaint();
}
}
class gegHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
//Here user input should be collected, placed in an array and
//saved in staafdiagram.setLengtes();
for (int i = 0; i < lengtes.length; i++){
lblNo.setText("Next Value Is " + i++);
lengtes[i] = Integer.parseInt( gegevensVak.getText());
gegevensVak.setText("");//clear textfield after entering a value
}
}
}
}
class Staafdiagram {
private int[] lengtes;
private int witruimte;//this generates the spaces between the bars
//First contructor with 2 arguments array en space
public Staafdiagram( int[] lengtes, int witruimte ) {
this.lengtes = lengtes;
this.witruimte = witruimte;
}
//Second constructor with only 1 argument space
public Staafdiagram(int witruimte ) {
this.witruimte = witruimte;
}
//With this, i want the user input to be collected in an array
public void setLengtes(int[] lengtes) {
this.lengtes = lengtes;
}
//To calculate the bar with the highest value
public int bepaalMax(){
int maximum = lengtes [0];
for (int i = 1; i < lengtes.length; i++){
if (lengtes[i] > maximum)
{
maximum = lengtes[i];
}
}
return maximum;
}
//To calculate the bar with the lowest value
public int bepaalMin(){
int minimum = lengtes [0];
for (int i = 1; i < lengtes.length; i++){
if (lengtes[i] < minimum)
{
minimum = lengtes[i];
}
}
return minimum;
}
public void teken( Graphics g, int x, int y ) {
int startX = x;
// Draw the bars
for( int lengte : lengtes ) {
if (lengte == bepaalMax())
g.setColor(Color.red);
else if (lengte == bepaalMin())
g.setColor(Color.green);
else
g.setColor(Color.black);
g.fillRect( x, y - 20 - lengte, 20, lengte );
x += witruimte;
}
// Display the values under the bars
x = startX;
for( int lengte : lengtes ) {
g.drawString( String.format( "%d", lengte ), x, y );
x += witruimte;
}
}
}

If you add an ActionListener on a JTextField, the actionPerformed() method is called when you "action" this field : here is the enter key pressed.
If you want associate the button to your action, you should rather enrich the ActionListener you defined on the JButton to also get the values entered by the user. The idea is chaining the both as both operations should performed one after the other one :
These values will be stored in an array and upon pressing the button,
a bar graph will be drawn to represent the entered values.
class BtnHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
// collection information from textfield
for (int i = 0; i < lengtes.length; i++){
lblNo.setText("Next Value Is " + i++);
lengtes[i] = Integer.parseInt( gegevensVak.getText());
gegevensVak.setText("");//clear textfield after entering a value
}
// rendering
staafdiagram = new Staafdiagram( lengtes, 30 );*/
repaint();
}
}

Get the input from the text field as text
split to string array
Convert to int
MOdify your code as follows.
class BtnHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
//To test using the first constructor. Works perfectly
/*int [] lengtes = { 144, 98, 117, 130, 172, 173 };
staafdiagram = new Staafdiagram( lengtes, 30 );*/
String textInt=gegevensVak .getText(); //gegevensVak is the name of the textfield you mentioned
String[] strArray = textInt.split();
//now convert the string to int and add to a new array
repaint();
}
}

How to account for input errors in calculator program?

I'm writing a calculator program for my java class. I want to account for errors like
User decides to divide by 0. I want the calculator to be able to acknowledge this error and display ERROR.
The user enters 6+7+ and then hits the equal button.
I want, once again, for the calculator to acknowledge that there is an error. I was hoping I could get some hints as to how to go about this. Thanks!
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class Calculator
{
JFrame window;
// stuff for top panel
JPanel topPanel;
JTextField expr,result;
JButton equals;
// stuff for bottom panel
JPanel bottomPanel,digitsPanel,opsPanel;
JButton[] digits,ops;
JButton clear, clearEntry;
Container content;
Listener listener;
String[] oplabels = { "+", "-", "/", "*" };
public Calculator()
{
listener = new Listener(); // our Listener class implements ActionListener
window= new JFrame("GUI Calc");
content=window.getContentPane();
content.setLayout( new GridLayout(2,1) );
topPanel=new JPanel();
topPanel.setLayout( new GridLayout(1,3) );
// TOP PANEL WORK
expr = new JTextField( );
equals = new JButton("=");
equals.addActionListener( listener );
result = new JTextField( );
topPanel.add( expr );
topPanel.add( equals );
topPanel.add( result );
// BOTTOM PANEL WORK
bottomPanel = new JPanel();
bottomPanel.setLayout( new GridLayout(1,2) );
digitsPanel = new JPanel();
digitsPanel.setLayout( new GridLayout(4,3) );
opsPanel = new JPanel();
opsPanel.setLayout( new GridLayout(4,1) );
digits = new JButton[12];
ops = new JButton[4];
for (int i=0 ; i<10 ; i++)
{
digits[i] = new JButton( i+"" );
digits[i].addActionListener(listener);
digitsPanel.add( digits[i] );
}
clear = new JButton( "C" );
clearEntry = new JButton( "CE" );
clear.addActionListener(listener);
clearEntry.addActionListener(listener);
digitsPanel.add( clear );
digitsPanel.add( clearEntry);
for (int i=0 ; i<4 ; i++)
{
ops[i] = new JButton( oplabels[i] ) ;
ops[i].addActionListener(listener);
opsPanel.add( ops[i] );
}
bottomPanel.add( digitsPanel );
bottomPanel.add( opsPanel );
content.add( topPanel);
content.add( bottomPanel);
window.setVisible(true);
}
class Listener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
Component clicked = (Component) e.getSource();
if ( clicked == equals )
{
result.setText( evaluate( expr.getText() ) );
return;
}
for ( int i=0 ; i<10 ; i++)
{
if ( clicked == digits[i] )
{
expr.setText( expr.getText() + i );
return;
}
}
if ( clicked == clear )
{
expr.setText("0");
return;
// do something
}
/* if (clicked == clearEntry)
{
expr.setText(expr.getDigits[i]);
}
for (int i=0; i < 10; i++)
{
if (clicked == digits[i])
{
int lastValue = clicked;
if(clicked == clearEntry)
{
expr.setText(expr.getText()-clicked);
return;
}
}
} */
for ( int i=0 ; i<4 ; i++ )
{
if(clicked == digits[i])
{
expr.setText(expr.getText() + oplabels[i]);
return;
}
// tack on that operator to the expr string
}
}
String evaluate( String exp )
{
return "NOT WRITTEN YET";
}
}
public static void main(String [] args)
{
new Calculator();
}
}
I'm still working on it. Especially where I'm trying to figure out the clearEntry button so I have put that section as a comment because its still a work in progress.

You can try this:
add a new class(Calculator) member:
Component last_clicked;
Inside Constructor:
last_clicked=null;
Before every return statement of actionPerformed, you can add this:
last_clicked=clicked;
Now, in actionPerformed method, when checking value of clicked, you can do this:
When clicked is '0' & last_clicked is '/', you can display error 1.
When clicked is 'equals' & last_clicked is an operator, you can display error 2.

Can someone help me work out the kinks in my program? [closed]

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Want to improve this question? Add details and clarify the problem by editing this post.
Closed 8 years ago.
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I have to write a calculator program using the Gui components. I have written the program but I'm having issues with my CE button. It is giving me errors. I'm also getting and error in my for loop where I add the operand labels to the expression. I was just hoping to get some help in fixing these errors. Thank you! Please ignore the comments. They are there for my to keep track of what I have to do.
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class Calculator
{
JFrame window;
// stuff for top panel
JPanel topPanel;
JTextField expr,result;
JButton equals;
// stuff for bottom panel
JPanel bottomPanel,digitsPanel,opsPanel;
JButton[] digits,ops;
JButton clear, clearEntry;
Container content;
Listener listener;
String[] oplabels = { "+", "-", "/", "*" };
public Calculator()
{
listener = new Listener(); // our Listener class implements ActionListener
window= new JFrame("GUI Calc");
content=window.getContentPane();
content.setLayout( new GridLayout(2,1) );
topPanel=new JPanel();
topPanel.setLayout( new GridLayout(1,3) );
// TOP PANEL WORK
expr = new JTextField( );
equals = new JButton("=");
equals.addActionListener( listener );
result = new JTextField( );
topPanel.add( expr );
topPanel.add( equals );
topPanel.add( result );
// BOTTOM PANEL WORK
bottomPanel = new JPanel();
bottomPanel.setLayout( new GridLayout(1,2) );
digitsPanel = new JPanel();
digitsPanel.setLayout( new GridLayout(4,3) );
opsPanel = new JPanel();
opsPanel.setLayout( new GridLayout(4,1) );
digits = new JButton[12];
ops = new JButton[4];
for (int i=0 ; i<10 ; i++)
{
digits[i] = new JButton( i+"" );
digits[i].addActionListener(listener);
digitsPanel.add( digits[i] );
}
clear = new JButton( "C" );
clearEntry = new JButton( "CE" );
clear.addActionListener(listener);
clearEntry.addActionListener(listener);
digitsPanel.add( clear );
digitsPanel.add( clearEntry);
for (int i=0 ; i<4 ; i++)
{
ops[i] = new JButton( oplabels[i] ) ;
ops[i].addActionListener(listener);
opsPanel.add( ops[i] );
}
bottomPanel.add( digitsPanel );
bottomPanel.add( opsPanel );
content.add( topPanel);
content.add( bottomPanel);
window.setVisible(true);
}
class Listener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
Component clicked = (Component) e.getSource();
if ( clicked == equals )
{
result.setText( evaluate( expr.getText() ) );
return;
}
for ( int i=0 ; i<10 ; i++)
{
if ( clicked == digits[i] )
{
expr.setText( expr.getText() + i );
return;
}
}
if ( clicked == clear )
{
expr.setText("0");
return;
// do something
}
for (int i=0; i < 10; i++)
{
if (clicked == digits[i])
{
int lastValue = i;
return;
}
}
if ( clicked == clearEntry )
{
expr.setText(expr.getText() - lastValue);
return;
// do something
}
for ( int i=0 ; i<4 ; i++ )
{
if(clicked == oplabels[i])
{
expr.setText(expr.getText + oplabels[i]);
return;
}
// tack on that operator to the expr string
}
}
String evaluate( String exp )
{
return "NOT WRITTEN YET";
}
}
public static void main(String [] args)
{
new Calculator();
}
}

Problem #1
The compiler is complaining about expr.setText(expr.getText() - lastValue); because lastValue is undefined.
Having a close look at the code, the only place that lastValue is defined is within the for-loop before the if statement...but the next issues thereturn` statement following it's decleration...
for (int i = 0; i < 10; i++) {
if (clicked == digits[i]) {
int lastValue = i;
return;
}
}
if (clicked == clearEntry) {
expr.setText(expr.getText() - lastValue);
return;
// do something
}
This not only makes the lastValue useless, but it's unlikely that the if statement would ever be reached...
Problem #2
for (int i = 0; i < 4; i++) {
if (clicked == oplabels[i]) {
expr.setText(expr.getText + oplabels[i]);
return;
}
// tack on that operator to the expr string
}
clicked is defined as Component clicked = (Component) e.getSource(); and oplables are defined as String[] oplabels = {"+", "-", "/", "*"};. String and Component are not comparable (also, you want expr.getText() not expr.getText).
I think you want to do something more like...
if (clicked instanceof JButton) {
JButton btn = (JButton)clicked)
for (int i = 0; i < oplabels.length; i++) {
if (oplabels[i].equals(btn.getText()) {
//...
}
}
}

Line 128: clicked is a Component and oplabels[i] is a string - you can't compare them directly.
Line 130: Missing () on getText() call.

show warning if users enter letter instead number in java applet

I am writing an tip calculator app in java applet with GUI, my question is how I make sure the error message will pop up if users enter letter instead of number
it is my first time asking question, please be easy on me! Thanks!!!
import objectdraw.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
// Typing in the text field and hitting return adds text to text area.
// Clicking on button erases the text area.
public class TextApplet extends Controller implements ActionListener
{
private static final int ROWS = 1; // rows in TextArea
private static final int COLS = 10; // cols in text field & area
private String amount;
private float number;
private JTextField inField, output; // Input field
private JButton clear, calc;
// button to clear output
public void begin()
{
Container contentPane = getContentPane();
JPanel topPanel = new JPanel(); // prepare text field & label
JLabel inLabel = new JLabel("Bill Cost: ");
inField = new JTextField(COLS);
inField.addActionListener(this);
JLabel topTitle = new JLabel("Tip Calculator", JLabel.CENTER);
JPanel combinePanel = new JPanel();
combinePanel.add ( inLabel );
combinePanel.add ( inField );
JPanel combinePanel1 = new JPanel();
combinePanel1.add ( topTitle );
topPanel.add ( combinePanel1 );
topPanel.add ( combinePanel );
topPanel.setLayout ( new GridLayout ( 3,1) );
contentPane.add(topPanel,BorderLayout.NORTH);
JPanel centerPanel = new JPanel(); // prepare text area & label
JLabel outLabel = new JLabel("Bill + Tip:");
output = new JTextField(COLS);
output.setEditable(false); // Prevent user from wrting in output
centerPanel.add(outLabel);
centerPanel.add(output);
contentPane.add(centerPanel,BorderLayout.CENTER);
JPanel bottomPanel = new JPanel();
// create button
clear = new JButton(" Clear ");
calc = new JButton("Calculate");
calc.addActionListener(this);
clear.addActionListener(this);
bottomPanel.add(calc);
bottomPanel.add(clear);
contentPane.add(bottomPanel,BorderLayout.SOUTH);
validate();
}
// add text to area if user hits return, else erase text area
public void actionPerformed(ActionEvent evt)
{
if (evt.getSource() == calc )
{
amount = inField.getText();
number = ( Float.parseFloat( amount ) );
number = (15*number/100);
output.setText ( Float.toString ( number ) + '$' );
}
else if (evt.getSource() == clear )
{
output.setText("$");
inField.setText("");
}
}
}

There are any number of ways you might achieve this, you could use
An InputVerifier
A JFormattedTextField
A JSpinner
Or a DocumentFilter and examples

Take a look at javax.swing.InputVerifier. That can be easily attached to a JTextField
JTextField inputField = new JTextField();
inputField.setInputVerifier(new NumericInputVerifier());
private class NumericInputVerifier extends InputVerifier
{
#Override
public boolean verify(JComponent input)
{
if (((JTextField) input).getText().matches("[0-9]+"))
{
return true;
}
else
{
JOptionPane.showMessageDialog(input, "Only numbers are allowed", "Warning", JOptionPane.WARNING_MESSAGE);
return false;
}
}
}
A complete example can be found here.
Edit Added an example of how to use InputVerifier to limit to numeric input. You'll want to double check the regex, but the basic idea is there...

Use a JFormattedTextField or a DocumentFilter. Then the user won't even be able to enter a non-numeric digit. See:
How to Use Formatted Text Fields
Implementing a Document Filter
For the document filter you will need to check each chraacter as it is entered to make sure it is a digit.
It is always better to do simple edits like that as the user types, rather than wait until you click on a button to do processing.

Hello Friend I will give a suggestion
please add validation when call actionPerformed method
public void actionPerformed(ActionEvent evt)
{
if (evt.getSource() == calc )
{
if(validate()){
amount = inField.getText();
number = ( Float.parseFloat( amount ) );
number = (15*number/100);
output.setText ( Float.toString ( number ) + '$' );
}
else{
// show message for inter valid number or any other
}
}
else if (evt.getSource() == clear )
{
output.setText("$");
inField.setText("");
}
}
boolean validate(){
try{
amount = inField.getText();
number = ( Float.parseFloat( amount ) );
return true;
}
catch(Exception e){
return false;
}
}

If you try to call Float.parseFloat on a String that cannot be converted to a float, it will throw a NumberFormatException. You need to catch this exception.
try {
number = ( Float.parseFloat( amount ) );
number = (15*number/100);
output.setText ( Float.toString ( number ) + '$' );
} catch(NumberFormatException e) {
//code to show error message here
}

Well considering, you'd have to turn the string into an integer to do the math, you could do this:
try {
int number = Ineger.parseInt(inField.getText());
} catch (NumberFormatException e) {
//SHOW WARNING
}

if (Label1.getText().matches("[0-9]+"))
// does Label1 containts numbers.
{
// do math
}
else
{
// warning
Lavbel1.setText("");
}

adding listeners to JButton array;

I have the following code which creates a JButton array on button click. Ope[] is publically declared in class. I have problem that I got null pointer. That is it doesn't print 2nd in loop ie. doesn't go in inner iteration.
Please tell me how to handle the listeners for array. Thanks in advance.
for( int i=0,y=30; i<counter;i++,y+=15 )
{
open[i]=new JButton( "Open" );
open[i].setBounds( 380, y, 70, 15 );
open[i].addActionListener( this );
panelDisplay.add (open[i] );
System.out.println(""+i);
}
The event handling in actionPerformed function is as follows:
for( int j=0; j<open.length; j++ )
{
System.out.println("1st in a loop"+j);
if( ae.getSource() != null )
{
if( ae.getSource() == open[j] )
{
System.out.println("2nd in a loop" +j);
int id;
String stringid;
System.out.println("open of"+j+"is clicked");
stringid = ""+table.getValueAt(j, 0);
id = Integer.parseInt(stringid);
fetchData(id);
//ae.getSource().equals(null);
}
}
}

JButton inherits "setName" Method from Component. So if you set a name on the Button at initialization
open[i]=new JButton( "Open" );
open[i].setBounds( 380, y, 70, 15 );
open[i].setName("Button"+i);
open[i].addActionListener( this );
panelDisplay.add (open[i] );
System.out.println(""+i);
you can find wich button was pressed in the eventhandling
int buttonNumber = Integer.parseInt(ae.getSource().getName().replace("Button",""))
//... do eventhandling for Button["buttonNumber"]