Qfyilyi

I have written the below code in Java to check for no entry by a user in JTextArea.
Only JTextArea.getText().equals("") works while others do not.
It would be of great help in case you can explain why other other checks don't work.

Thanks

import java.util.*;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;



class TestJTextArea{

  private JFrame frame;

  private JPanel panel;

  private JLabel textLabel;

  private JTextArea textArea;

  private JButton submitButton;



  public TestJTextArea(){

    frame = new JFrame("Test JTextArea");

    panel = new JPanel();

    textLabel = new JLabel("Enter your Text below");

    textArea = new JTextArea(20,20);

    submitButton = new JButton("Submit");



    setupGUI();

  }



  private void setupGUI(){

    textArea.setLineWrap(true);

    textArea.setWrapStyleWord(true);

    JScrollPane scrollPane = new JScrollPane(textArea);

    scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

    scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);



    textArea.setFont(new Font("sansserif", Font.BOLD, 24));



    panel.setLayout(new BoxLayout(panel,BoxLayout.Y_AXIS));

    panel.add(textLabel);

    panel.add(scrollPane);

    panel.add(submitButton);

    submitButton.addActionListener(new SubmitButtonListener());



    frame.setSize(200,200);

    frame.getContentPane().add(BorderLayout.CENTER,panel);

    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    frame.setVisible(true);

  }



  private class SubmitButtonListener implements ActionListener{

    public void actionPerformed(ActionEvent e){

Check for equals("") works. So the below code throws True:

if(textArea.getText().equals("")){

        JOptionPane.showMessageDialog(null,"No Text test True for equals()","Check equality through equals()",JOptionPane.WARNING_MESSAGE);

      }

      else

        JOptionPane.showMessageDialog(null,"No Text test False for equals()","Check equality through equals()",JOptionPane.WARNING_MESSAGE);

The below code throws False:

  if(textArea.getText() == ""){

    JOptionPane.showMessageDialog(null,"No Text test True for ==","Check equality through ==",JOptionPane.WARNING_MESSAGE);

  }      

  else

    JOptionPane.showMessageDialog(null,"No Text test False for ==","Check equality through ==",JOptionPane.WARNING_MESSAGE);

The below code throws False:

 if(textArea.getText() == null){

    JOptionPane.showMessageDialog(null,"No Text test True for null","Check equality through null",JOptionPane.WARNING_MESSAGE);

  }      

  else

    JOptionPane.showMessageDialog(null,"No Text test False for null","Check equality through null",JOptionPane.WARNING_MESSAGE);

All the below Codes throw False:

  if(textArea.getText().toString() == ""){

    JOptionPane.showMessageDialog(null,"No Text test True for toString()","Check equality through toString()",JOptionPane.WARNING_MESSAGE);

  }      

  else

    JOptionPane.showMessageDialog(null,"No Text test False for toString()","Check equality through toString()",JOptionPane.WARNING_MESSAGE);



  if(textArea.getText().toString() == null){

    JOptionPane.showMessageDialog(null,"No Text test True for toString() = null","Check equality through toString() = null",JOptionPane.WARNING_MESSAGE);

  }      

  else

    JOptionPane.showMessageDialog(null,"No Text test False for toString() = null","Check equality through toString() = null",JOptionPane.WARNING_MESSAGE);

Comparing String with == operator will compare references, that means it will work only if it is same String instance. To check if values of the Strings are the same, you should always use equals method.

Good approach is to use StringUtils methods IsEmpty/IsBlank - checks if a String contains text https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html