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8223775: String::stripIndent (Preview)

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Reviewed-by: abuckley, vromero, jlahoda, bchristi, rriggs, smarks
This commit is contained in:
Jim Laskey 2019-06-06 12:24:44 -03:00
parent 618afc3fa2
commit 0777a86d68
4 changed files with 185 additions and 148 deletions
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135
src/java.base/share/classes/java/lang/String.java
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@ -36,6 +36,7 @@ import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Formatter;
import java.util.List;
import java.util.Locale;
import java.util.Objects;
import java.util.Optional;
@ -2797,11 +2798,6 @@ public final class String
return indexOfNonWhitespace() == length();
}
private Stream<String> lines(int maxLeading, int maxTrailing) {
return isLatin1() ? StringLatin1.lines(value, maxLeading, maxTrailing)
: StringUTF16.lines(value, maxLeading, maxTrailing);
}
/**
* Returns a stream of lines extracted from this string,
* separated by line terminators.
@ -2833,7 +2829,7 @@ public final class String
* @since 11
*/
public Stream<String> lines() {
return lines(0, 0);
return isLatin1() ? StringLatin1.lines(value) : StringUTF16.lines(value);
}
/**
@ -2873,12 +2869,10 @@ public final class String
* @since 12
*/
public String indent(int n) {
return isEmpty() ? "" : indent(n, false);
}
private String indent(int n, boolean removeBlanks) {
Stream<String> stream = removeBlanks ? lines(Integer.MAX_VALUE, Integer.MAX_VALUE)
: lines();
if (isEmpty()) {
return "";
}
Stream<String> stream = lines();
if (n > 0) {
final String spaces = " ".repeat(n);
stream = stream.map(s -> spaces + s);
@ -2900,6 +2894,123 @@ public final class String
: StringUTF16.lastIndexOfNonWhitespace(value);
}
/**
* Returns a string whose value is this string, with incidental
* {@linkplain Character#isWhitespace(int) white space} removed from
* the beginning and end of every line.
* <p>
* Incidental {@linkplain Character#isWhitespace(int) white space}
* is often present in a text block to align the content with the opening
* delimiter. For example, in the following code, dots represent incidental
* {@linkplain Character#isWhitespace(int) white space}:
* <blockquote><pre>
* String html = """
* ..............&lt;html&gt;
* .............. &lt;body&gt;
* .............. &lt;p&gt;Hello, world&lt;/p&gt;
* .............. &lt;/body&gt;
* ..............&lt;/html&gt;
* ..............""";
* </pre></blockquote>
* This method treats the incidental
* {@linkplain Character#isWhitespace(int) white space} as indentation to be
* stripped, producing a string that preserves the relative indentation of
* the content. Using | to visualize the start of each line of the string:
* <blockquote><pre>
* |&lt;html&gt;
* | &lt;body&gt;
* | &lt;p&gt;Hello, world&lt;/p&gt;
* | &lt;/body&gt;
* |&lt;/html&gt;
* </pre></blockquote>
* First, the individual lines of this string are extracted as if by using
* {@link String#lines()}.
* <p>
* Then, the <i>minimum indentation</i> (min) is determined as follows.
* For each non-blank line (as defined by {@link String#isBlank()}), the
* leading {@linkplain Character#isWhitespace(int) white space} characters are
* counted. The leading {@linkplain Character#isWhitespace(int) white space}
* characters on the last line are also counted even if
* {@linkplain String#isBlank() blank}. The <i>min</i> value is the smallest
* of these counts.
* <p>
* For each {@linkplain String#isBlank() non-blank} line, <i>min</i> leading
* {@linkplain Character#isWhitespace(int) white space} characters are removed,
* and any trailing {@linkplain Character#isWhitespace(int) white space}
* characters are removed. {@linkplain String#isBlank() Blank} lines are
* replaced with the empty string.
*
* <p>
* Finally, the lines are joined into a new string, using the LF character
* {@code "\n"} (U+000A) to separate lines.
*
* @apiNote
* This method's primary purpose is to shift a block of lines as far as
* possible to the left, while preserving relative indentation. Lines
* that were indented the least will thus have no leading
* {@linkplain Character#isWhitespace(int) white space}.
* The line count of the result will be the same as line count of this
* string.
* If this string ends with a line terminator then the result will end
* with a line terminator.
*
* @implNote
* This method treats all {@linkplain Character#isWhitespace(int) white space}
* characters as having equal width. As long as the indentation on every
* line is consistently composed of the same character sequences, then the
* result will be as described above.
*
* @return string with incidental indentation removed and line
* terminators normalized
*
* @see String#lines()
* @see String#isBlank()
* @see String#indent(int)
* @see Character#isWhitespace(int)
*
* @since 13
*
* @deprecated This method is associated with text blocks, a preview language feature.
* Text blocks and/or this method may be changed or removed in a future release.
*/
@Deprecated(forRemoval=true, since="13")
public String stripIndent() {
int length = length();
if (length == 0) {
return "";
}
char lastChar = charAt(length - 1);
boolean optOut = lastChar == '\n' || lastChar == '\r';
List<String> lines = lines().collect(Collectors.toList());
final int outdent = optOut ? 0 : outdent(lines);
return lines.stream()
.map(line -> {
int firstNonWhitespace = line.indexOfNonWhitespace();
int lastNonWhitespace = line.lastIndexOfNonWhitespace();
int incidentalWhitespace = Math.min(outdent, firstNonWhitespace);
return firstNonWhitespace > lastNonWhitespace
? "" : line.substring(incidentalWhitespace, lastNonWhitespace);
})
.collect(Collectors.joining("\n", "", optOut ? "\n" : ""));
}
private static int outdent(List<String> lines) {
// Note: outdent is guaranteed to be zero or positive number.
// If there isn't a non-blank line then the last must be blank
int outdent = Integer.MAX_VALUE;
for (String line : lines) {
int leadingWhitespace = line.indexOfNonWhitespace();
if (leadingWhitespace != line.length()) {
outdent = Integer.min(outdent, leadingWhitespace);
}
}
String lastLine = lines.get(lines.size() - 1);
if (lastLine.isBlank()) {
outdent = Integer.min(outdent, lastLine.length());
}
return outdent;
}
/**
* This method allows the application of a function to {@code this}
* string. The function should expect a single String argument