[英]System.getProperty(“line.separator”) Vs “\n” for Android
[英]Java: Why checking for “\n” doesn't match new lines added using System.getProperty(“line.separator”)
( 更新的问题 )
首先,我认为"\\n"
等同于System.getProperty("line.separator")
我写了一些与Strings一起使用的方法,其中一些方法检查是否存在新行
if (string.charAt(i) == '\\n') {//do something;}
但是我注意到检查"\\n"
与System.getProperty("line.separator")
添加的新行不匹配
这是一个SSCCE来证明我的主张!:
描述:
两串相同的文字; 一个alpha_String
使用"\\n"
添加新行,另一个beta_String
使用System.getProperty("line.separator")
添加新行
有一个名为String removeExtraNewLines(String)
用于删除String removeExtraNewLines(String)
中的任何额外新行并将其返回; 正如其标题所示。 使用此方法过滤了两个字符串。
两个按钮buttonAlpha
和buttonBeta
每个设置的文本JTextArea
与过滤的字符串
您会注意到方法捕获/匹配并删除额外的新行alpha_String
但不会对alpha_String
执行相同beta_String
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 < myNewString.length(); i++)
{
if (i > 1)
{
previouseChar = myNewString.charAt(i - 1);
}
if ((myNewString.charAt(i) == '\n') && (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();
}
});
}
}
所以问题 :为什么检查"\\n"
与使用System.getProperty("line.separator")
添加的新行不匹配?,以及如何匹配它们?
首先,我认为“\\ n”等同于System.getProperty(“line.separator”),除了后者与平台无关。
不,后者是特定于平台的 。 这是获取平台线分隔符的独立于平台的方式。
所以在Windows上,我希望System.getProperty("line.separator")
返回“\\ r \\ n”,例如。
现在关于textArea
用于换行的内容 - 完全取决于textArea
是什么 - 并且您没有向我们提供任何相关信息。
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