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Text word wrapping in Java
package org.davidmoten.text.utils;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.HashSet;
import java.util.Set;
import java.util.function.Function;
import com.github.davidmoten.guavamini.Preconditions;
import com.github.davidmoten.guavamini.annotations.VisibleForTesting;
public final class WordWrap {
private WordWrap() {
// prevent instantiation
}
private static final String SPECIAL_WORD_CHARS = "\"\'\u2018\u2019\u201C\u201D?./!,;:_";
public static final Set SPECIAL_WORD_CHARS_SET_DEFAULT = toSet(SPECIAL_WORD_CHARS);
private static final Function STRING_WIDTH_DEFAULT = s -> s.length();
private static final String PUNCTUATION = "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~";
/**
* Sets the source to be wrapped and returns a builder to specify more
* parameters.
*
* @param reader source to be wrapped
* @return builder
*/
public static Builder from(Reader reader) {
return from(reader, false);
}
/**
* Sets the source to be wrapped as a classpath resource which will be read
* using the UTF-8 character set. Returns a builder to specify more parameters.
* Uses an 8192 byte buffer for reading.
*
* @param resource source to be wrapped as a classpath resource
* @return builder
*/
public static Builder fromClasspathUtf8(String resource) {
return fromClasspath(resource, StandardCharsets.UTF_8);
}
/**
* Sets the source to be wrapped as a classpath resource to be read using the
* given character set. Returns a builder to specify more parameters. Uses an
* 8192 byte buffer for reading.
*
* @param resource classpath resource name
* @param charset charset to use for reading
* @return builder
*/
public static Builder fromClasspath(String resource, Charset charset) {
return new Builder(
new BufferedReader(new InputStreamReader(WordWrap.class.getResourceAsStream(resource), charset)), true);
}
/**
* Sets the the source to be wrapped and returns a builder to specify more
* parameters. Uses an 8192 byte buffer for reading.
*
* @param text text to be wrapped
* @return builder
*/
public static Builder from(CharSequence text) {
return from(new BufferedReader(new CharSequenceReader(text)), true);
}
/**
* Sets the source to be wrapped. Returns a builder to specify more parameters.
* Uses an 8192 byte buffer for reading.s
*
* @param in source to be wrapped
* @return builder
*/
public static Builder fromUtf8(InputStream in) {
return from(in, StandardCharsets.UTF_8);
}
/**
* Sets the source to be wrapped and the character set to be used to read it.
* Uses an 8192 byte buffer for reading. Returns a builder to specify more
* parameters.
*
* @param in source to be wrapped
* @param charset encoding
* @return builder
*/
public static Builder from(InputStream in, Charset charset) {
return from(new BufferedReader(new InputStreamReader(in, charset)));
}
/**
* Sets the source to be wrapped and the character set to be used to read it.
* Uses an 8192 byte buffer for reading. Returns a builder to specify more
* parameters.
*
* @param file file to be read
* @param charset charset of the text in the source file
* @return builder
*/
public static Builder from(File file, Charset charset) {
try {
return from(new BufferedReader(new InputStreamReader(new FileInputStream(file), charset)), true);
} catch (FileNotFoundException e) {
throw new IORuntimeException(e);
}
}
private static Builder from(Reader reader, boolean close) {
return new Builder(reader, close);
}
/**
* Provides method chaining for specifying parameters to word wrap.
*/
public static final class Builder {
private final Reader reader;
private final boolean closeReader;
private Number maxWidth = 80;
private Function stringWidth = STRING_WIDTH_DEFAULT;
private Set extraWordChars = SPECIAL_WORD_CHARS_SET_DEFAULT;
private String newLine = "\n";
private boolean insertHyphens = true;
private boolean breakWords = true;
Builder(Reader reader, boolean closeReader) {
this.reader = reader;
this.closeReader = closeReader;
}
/**
* Sets the maximum width of a line using the {@code stringWidth} function. Word
* wrapping/splitting will be attempted for lines with greater than
* {@code maxWidth}. If not set the default is 80.
*
* @param maxWidth maximum width of a line using the {@code stringWidth}
* function.
* @return this
* @throws IllegalArgumentException if {@code maxWidth} is less than or equal to
* zero
*/
public Builder maxWidth(Number maxWidth) {
Preconditions.checkArgument(maxWidth.doubleValue() > 0);
this.maxWidth = maxWidth;
return this;
}
/**
* Sets the string width function used to determine if a line is at maximum
* width (and therefore needing wrapping or splitting). If not set the string
* width function is the number of characters.
*
* @param stringWidth function that returns the width of a sequence of
* characters
* @return this
*/
public Builder stringWidth(Function stringWidth) {
this.stringWidth = stringWidth;
return this;
}
/**
* Sets the newLine string to be used. If not set the default is '\n' (line feed
* character).
*
* @param newLine string to be output on for a new line delimiter
* @return this
*/
public Builder newLine(String newLine) {
this.newLine = newLine;
return this;
}
/**
* Sets all extra word characters (characters that will be treated like normal
* alphabetic characters for defining word boundaries).
*
* @param extraWordChars extra word characters (in addtion to alphabetic
* characters)
* @return this
*/
public Builder extraWordChars(Set extraWordChars) {
this.extraWordChars = extraWordChars;
return this;
}
/**
* Sets all extra word characters (characters that will be treated like normal
* alphabetic characters for defining word boundaries).
*
* @param extraWordChars extra word characters (in addtion to alphabetic
* characters)
* @return this
*/
public Builder extraWordChars(String extraWordChars) {
return extraWordChars(toSet(extraWordChars));
}
/**
* Adds more word characters (characters that will be treated like normal
* alphabetic characters for defining word boundaries).
*
* @param includeWordChars more word characters
* @return this
*/
public Builder includeExtraWordChars(String includeWordChars) {
Set set = toSet(includeWordChars);
this.extraWordChars.addAll(set);
return this;
}
/**
* Adds extra word characters to be excluded. Alphabetic characters are always
* word characters and thus will be ignored here.
*
* @param excludeWordChars extra word characters to be excluded
* @return this
*/
public Builder excludeExtraWordChars(String excludeWordChars) {
Set set = toSet(excludeWordChars);
this.extraWordChars.removeAll(set);
return this;
}
/**
* Sets if to break words using a hyphen character. If set to false then no
* breaking character will be used.
*
* @param insertHyphens whether to break hyphens
* @return this
*/
public Builder insertHyphens(boolean insertHyphens) {
this.insertHyphens = insertHyphens;
return this;
}
/**
* If a word is longer than {@code maxWidth} and {@code breakWords} is true then
* such a word will be broken across two or more lines (with or without a hyphen
* according to {@link Builder#insertHyphens(boolean)}).
*
* @param breakWords if true then break words across lines
* @return this
*/
public Builder breakWords(boolean breakWords) {
this.breakWords = breakWords;
return this;
}
/**
* Performs the wrapping of the source text and writes output to the given
* {@link Writer}.
*
* @param out output for wrapped text
*/
public void wrap(Writer out) {
try {
wordWrap(reader, out, newLine, maxWidth, stringWidth, extraWordChars, insertHyphens, breakWords);
} catch (IOException e) {
throw new IORuntimeException(e);
} finally {
if (closeReader) {
close(reader);
}
}
}
/**
* Performs the wrapping of the source text and writes output to the given file
* with the given character set encoding.
*
* @param file file to receive wrapped output
* @param charset encoding to use for output
*/
public void wrap(File file, Charset charset) {
try (Writer writer = new OutputStreamWriter(new FileOutputStream(file), charset)) {
wrap(writer);
} catch (IOException e) {
throw new IORuntimeException(e);
}
}
/**
* Performs the wrapping of the source text and writes the output to the given
* file using UTF-8 encoding.
*
* @param file output file for wrapped text
*/
public void wrapUtf8(File file) {
wrap(file, StandardCharsets.UTF_8);
}
/**
* Performs the wrapping of the source text and writes the output to a file with
* the given filename.
*
* @param filename output file for wrapped text
*/
public void wrapUtf8(String filename) {
wrapUtf8(new File(filename));
}
/**
* Performs the wrapping of the source text and writes the output to a file with
* the given filename using the given encoding.
*
* @param filename output file for the wrapped text
* @param charset encoding to use for output
*/
public void wrap(String filename, Charset charset) {
wrap(new File(filename), charset);
}
/**
* Performs the wrapping of the source text and returns output as a String.
*
* @return wrapped text
*/
public String wrap() {
try (StringWriter out = new StringWriter()) {
wrap(out);
return out.toString();
} catch (IOException e) {
throw new IORuntimeException(e);
}
}
}
@VisibleForTesting
static void close(Reader reader) {
try {
reader.close();
} catch (IOException e) {
throw new IORuntimeException(e);
}
}
private static Set toSet(String chars) {
Set set = new HashSet();
for (int i = 0; i < chars.length(); i++) {
set.add(chars.charAt(i));
}
return set;
}
static void wordWrap(Reader in, Writer out, String newLine, Number maxWidth,
Function stringWidth, Set extraWordChars,
boolean insertHyphens, boolean breakWords) throws IOException {
StringBuilder2 line = new StringBuilder2();
StringBuilder2 word = new StringBuilder2();
CharSequence lineAndWordRightTrim = concatRightTrim(line, word);
double maxWidthDouble = maxWidth.doubleValue();
boolean broken = false;
boolean isWordCharacter = false;
boolean previousWasPunctuation = false;
while (true) {
int c = in.read();
if (c == -1) {
break;
}
char ch = (char) c;
isWordCharacter = Character.isLetter(ch) || extraWordChars.contains(ch);
if (ch == '\n') {
line.append(word);
if (tooLong(stringWidth, line, maxWidthDouble)) {
line.rightTrim();
}
if (!isWhitespace(line)) {
out.write(line.internalArray(), 0, line.length());
}
out.write(newLine);
word.setLength(0);
line.setLength(0);
broken = false;
} else if (ch == '\r') {
// ignore carriage return
} else if (isWordCharacter && !previousWasPunctuation) {
word.append(ch);
if (broken && line.length() == 0) {
leftTrim(word);
}
if (tooLong(stringWidth, lineAndWordRightTrim, maxWidthDouble)) {
if (line.length() > 0) {
writeLine(out, line, newLine);
leftTrim(word);
if (tooLong(stringWidth, word, maxWidthDouble)) {
if (breakWords) {
writeBrokenWord(out, word, newLine, insertHyphens);
} else {
broken = true;
}
} else {
broken = true;
}
} else {
if (breakWords) {
writeBrokenWord(out, word, newLine, insertHyphens);
} else {
broken = true;
}
}
}
} else {
if (word.length() > 0 && !isWhitespace(word)) {
appendWordToLine(line, word);
if (broken) {
leftTrim(line);
}
}
word.append(ch);
if (tooLong(stringWidth, lineAndWordRightTrim, maxWidthDouble)) {
Preconditions.checkArgument(line.length() > 0, "line length was zero. If this happens please" //
+ " contribute unit test that provokes this failure to the project!");
if (!isWhitespace(line)) {
writeLine(out, line, newLine);
} else {
line.setLength(0);
}
broken = true;
}
}
previousWasPunctuation = isPunctuation(ch) && !extraWordChars.contains(ch);
}
if (line.length() > 0) {
String s = line.toString() + word.toString();
if (broken) {
s = leftTrim(s);
}
out.write(s);
} else {
if (broken) {
leftTrim(word);
}
if (!isWhitespace(word)) {
out.write(word.internalArray(), 0, word.length());
}
}
}
private static CharSequence concatRightTrim(CharSequence a, CharSequence b) {
return new CharSequenceConcatRightTrim(a, b);
}
private static boolean isPunctuation(char ch) {
return PUNCTUATION.indexOf(ch) != -1;
}
private static boolean tooLong(Function stringWidth, CharSequence s,
double maxWidthDouble) {
return stringWidth.apply(s).doubleValue() > maxWidthDouble;
}
@VisibleForTesting
static CharSequence rightTrim(CharSequence s) {
int i = s.length();
while (i > 0) {
if (Character.isWhitespace(s.charAt(i - 1))) {
i--;
} else {
break;
}
}
if (i != s.length()) {
return s.subSequence(0, i);
} else {
return s;
}
}
static boolean isWhitespace(CharSequence s) {
for (int i = 0; i < s.length(); i++) {
if (!Character.isWhitespace(s.charAt(i))) {
return false;
}
}
return true;
}
@VisibleForTesting
static void leftTrim(StringBuilder2 word) {
// trim leading spaces on the word
// because we have inserted a new line
int i;
for (i = 0; i < word.length(); i++) {
if (!Character.isWhitespace(word.charAt(i))) {
break;
}
}
if (i < word.length() && i > 0) {
word.delete(0, i);
}
}
private static String leftTrim(String s) {
StringBuilder2 b = new StringBuilder2(s);
leftTrim(b);
return b.toString();
}
private static void appendWordToLine(StringBuilder2 line, StringBuilder2 word) {
line.append(word);
word.setLength(0);
}
private static void writeBrokenWord(Writer out, StringBuilder2 word, String newLine, boolean insertHyphens)
throws IOException {
// to be really thorough we'd check the new stringWidth with '-' but let's not
// bother for now
String x;
if (insertHyphens && word.length() > 2 && !isWhitespace((x = word.substring(0, word.length() - 2)))) {
out.write(x);
out.write("-");
out.write(newLine);
word.delete(0, word.length() - 2);
} else {
String prefix = word.substring(0, word.length() - 1);
if (!isWhitespace(prefix)) {
out.write(prefix);
}
out.write(newLine);
word.delete(0, word.length() - 1);
}
}
private static void writeLine(Writer out, StringBuilder2 line, String newLine) throws IOException {
out.write(line.internalArray(), 0, line.length());
out.write(newLine);
line.setLength(0);
}
}
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