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POJava: Why checking for "\n" doesn't match new lines added using System.getProperty("line.separator")
 

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  1. POJava: Why checking for "\n" doesn't match new lines added using System.getProperty("line.separator")
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    <p>(<strong>Updated Question</strong>)</p> <p>First, I think that <code>"\n"</code> is equivalent to <code>System.getProperty("line.separator")</code></p> <p>I wrote some methods to work with Strings some of them check for existence of new line</p> <p><code>if (string.charAt(i) == '\n') {//do something;}</code></p> <p>But I noticed that checking for <code>"\n"</code> doesn't match the new lines added by the <code>System.getProperty("line.separator")</code></p> <p>This is an <strong>SSCCE</strong> to demonstrate my claim!:</p> <p><strong>Description:</strong><br> Two strings of identical text; one <code>alpha_String</code> has new lines added using <code>"\n"</code>, and the other <code>beta_String</code> has new lines added using <code>System.getProperty("line.separator")</code></p> <p>There is a method named <code>String removeExtraNewLines(String)</code> used to remove any extra new lines in a String and return it back; as its header suggests. The two strings filtered using this method.</p> <p>The two buttons <code>buttonAlpha</code> and <code>buttonBeta</code> each set the text of the <code>JTextArea</code> with the filtered String</p> <p><strong>You will notice</strong> that the the method catch/match and remove extra new lines of <code>alpha_String</code> but don't do the same with <code>beta_String</code></p> <pre><code>import java.awt.BorderLayout; import java.awt.event.ActionEvent; import javax.swing.*; public class NewLineTest extends JPanel { JPanel buttonPanel; JPanel textAreaPanel; JButton buttonAlpha; JButton buttonBeta; JTextArea textArea; String n = "\n"; String s = System.getProperty("line.separator"); String alpha_String; String beta_String; public NewLineTest() { createSentencesText(); buttonAlpha = new JButton("Alpha String"); buttonAlpha.addActionListener(eventWatcher); buttonBeta = new JButton("Beta String"); buttonBeta.addActionListener(eventWatcher); textArea = new JTextArea(0, 0); JScrollPane scrollTextArea = new JScrollPane(textArea); scrollTextArea.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS); textArea.setEditable(false); buttonPanel = new JPanel(); textAreaPanel = new JPanel(new BorderLayout()); buttonPanel.add(buttonAlpha); buttonPanel.add(buttonBeta); textAreaPanel.add(scrollTextArea, BorderLayout.CENTER); JSplitPane splitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, textAreaPanel, buttonPanel); splitPane.setDividerLocation(400); splitPane.setResizeWeight(.5d); this.setLayout(new BorderLayout()); this.add(splitPane); } private void createSentencesText() { alpha_String = "A: Let’s go to the beach." + n + n + "B: That’s a great idea." + n + "A: We haven’t been in a while." + n + n + "B: We haven’t been in a month." + n + "A: The last time we went, you almost drowned." + n + "B: No, I didn’t." + n + n + n + "A: Then why did the lifeguard dive into the water?" + n + "B: I think he wanted to cool off." + n + "A: He swam right up to you." + n + "B: And then he turned right around." + n + "A: Maybe you’re right." + n + "B: Maybe we should get going."; beta_String = "A: Let’s go to the beach." + s + s + "B: That’s a great idea." + s + "A: We haven’t been in a while." + s + s + "B: We haven’t been in a month." + s + "A: The last time we went, you almost drowned." + s + "B: No, I didn’t." + s + s + s + "A: Then why did the lifeguard dive into the water?" + s + "B: I think he wanted to cool off." + s + "A: He swam right up to you." + s + "B: And then he turned right around." + s + "A: Maybe you’re right." + s + "B: Maybe we should get going."; } public static String removeExtraNewLines(String s) { String myNewString = s.trim(); StringBuilder stringB = new StringBuilder(); char previouseChar = '~'; for (int i = 0; i &lt; myNewString.length(); i++) { if (i &gt; 1) { previouseChar = myNewString.charAt(i - 1); } if ((myNewString.charAt(i) == '\n') &amp;&amp; (previouseChar == '\n')) { continue; } stringB.append(myNewString.charAt(i)); } myNewString = stringB.toString(); return myNewString; } AbstractAction eventWatcher = new AbstractAction() { @Override public void actionPerformed(ActionEvent ae) { Object source = ae.getSource(); if (source == buttonAlpha) { String arranged_string_alpha = removeExtraNewLines(alpha_String); textArea.setText(arranged_string_alpha); } if (source == buttonBeta) { String arranged_string_beta = removeExtraNewLines(beta_String); textArea.setText(arranged_string_beta); } } }; private static void createAndShowGUI() { JFrame frame = new JFrame("NewLine Test"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(700, 300); frame.add(new NewLineTest(), BorderLayout.CENTER); frame.setVisible(true); } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { UIManager.put("swing.boldMetal", Boolean.FALSE); createAndShowGUI(); } }); } } </code></pre> <p><strong>So the question</strong>: Why checking for <code>"\n"</code> doesn't match new lines added using <code>System.getProperty("line.separator")</code>?, And How to match them?</p>
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    1. COHave you verified that on your system, the System constant is in fact equal to `'\n'`? It shouldn't take more than a simple comparison to discover, right?
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    2. COFirst of all, which OS are you using to test this? Second, does `if (string.charAt(i) == System.getProperty("line.separator"))` not work as you expect? Third, have you tried using a debugger to examine what the value of `System.getProperty("line.separator")` actually is?
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      1. POJava: Why checking for "\n" doesn't match new lines added using System.getProperty("line.separator")
      1. USJesse Webb
    3. COThis article may interest you http://en.wikipedia.org/wiki/Newline
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