Detail This method replaces all sequences of one or more whitespace with a space. It normalizes spacing in a string.
public class Program {
static String removeAllWhitespace(String value) {
// Remove all whitespace characters.
return value.replaceAll("\\s", "");
}
static String collapseWhitespace(String value) {
// Replace all whitespace blocks with single spaces.
return value.replaceAll("\\s+", " ");
}
public static void main(String[] args) {
String value = " Hi,\r\n\t\tA B C";
// Test our methods.
String result = removeAllWhitespace(value);
System.out.println(result);
result = collapseWhitespace(value);
System.out.println(result);
}
}Hi,ABC
Hi, A B C
Convert with toCharArray. This example uses another approach to whitespace. It converts a String to a char array and changes the array's elements.
Result The method changes common whitespace characters all into spaces. This algorithm may perform faster than a regular expression.
public class Program {
static String convertWhitespaceToSpaces(String value) {
// Convert String to a character array.
char[] array = value.toCharArray();
for (int i = 0; i < array.length; i++) {
// Modify all newlines and tabs to be spaces.
switch (array[i]) {
case '\r':
case '\n':
case '\t':
array[i] = ' ';
break;
}
}
// Return the modified string.
return new String(array);
}
public static void main(String[] args) {
String value = "A B\nC D\tE F";
// Test the conversion method.
System.out.println(convertWhitespaceToSpaces(value));
}
}A B C D E F
Convert to UNIX newlines. UNIX uses just one character, \n for newlines. But Windows uses two—the \r\n sequence. We can convert Windows newlines to UNIX ones.
Result This program changes the two Windows newline sequences but leaves the UNIX one alone. So the String length is reduced by 2 chars.
public class Program {
static String convertToUNIXNewlines(String value) {
// Normalize the newlines in the String.
return value.replace("\r\n", "\n");
}
public static void main(String[] args) {
// This string contains both Windows and UNIX newlines.
String value = "A B\r\nC\r\nD\nE";
// Replace Windows newlines.
String result = convertToUNIXNewlines(value);
// Write length before and after.
System.out.println(value.length());
System.out.println(result.length());
}
}11
9
Convert to Windows newlines. This method handles the reverse conversion: it converts from UNIX to Windows newlines. This is more complex.
Start We normalize all newlines to UNIX newlines. In this way we avoid corrupting existing newlines.
Then We change all UNIX newlines to Windows newlines. The final String has the correct number of newline chars.
public class Program {
static String convertToUNIXNewlines(String value) {
return value.replace("\r\n", "\n");
}
static String convertToWindowsNewlines(String value) {
// Convert to UNIX lines to normalize all newlines.// ... Then replace with Windows newlines.
value = convertToUNIXNewlines(value);
return value.replace("\n", "\r\n");
}
public static void main(String[] args) {
// This string contains 2 UNIX newlines.
String value = "Cat\nDog\nFish\r\nBird";
String result = convertToWindowsNewlines(value);
// Write lengths.// ... The two UNIX newlines were converted.// ... The Windows newline was ignored.
System.out.println(value.length());
System.out.println(result.length());
}
}18
20
Convert file newlines. This program converts a file's newlines to UNIX newlines. It reads the file in as a byte array and converts it to a string.
Warning This program is not perfect. It is slower than ideal and may cause some encoding issues.
Detail The program converts the String back into a byte array and writes it to the same location, replacing the original file.
import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
public class Program {
static String convertToUNIXNewlines(String value) {
return value.replace("\r\n", "\n");
}
public static void main(String[] args) throws IOException {
// Get a Path object.
Path path = FileSystems.getDefault().getPath("C:\\programs\\file.txt");
// Read all bytes for the file and convert it to a string.
byte[] data = Files.readAllBytes(path);
String data2 = new String(data);
// Fix newlines.
data2 = convertToUNIXNewlines(data2);
// Write converted bytes.
byte[] data3 = data2.getBytes();
Files.write(path, data3);
}
}
Trim. For leading or trailing spaces, the trim() method is ideal. It does not require any special code. This is like a chomp() or chop() method in other languages.
Summary. In processing text, we remove or combine whitespace. These methods help with that task. Further steps may (for example) remove stopwords.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.