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src/java.base/share/classes/java/lang/String.java
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rev 54939 : 8223775: String::stripIndent (Preview)
@@ -34,10 +34,11 @@
import java.nio.charset.Charset;
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;
import java.util.Spliterator;
import java.util.StringJoiner;
@@ -2795,15 +2796,10 @@
*/
public boolean isBlank() {
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.
* <p>
* A <i>line terminator</i> is one of the following:
@@ -2831,11 +2827,11 @@
* @return the stream of lines extracted from this string
*
* @since 11
*/
public Stream<String> lines() {
- return lines(0, 0);
+ return isLatin1() ? StringLatin1.lines(value) : StringUTF16.lines(value);
}
/**
* Adjusts the indentation of each line of this string based on the value of
* {@code n}, and normalizes line termination characters.
@@ -2871,16 +2867,14 @@
* @see Character#isWhitespace(int)
*
* @since 12
*/
public String indent(int n) {
- return isEmpty() ? "" : indent(n, false);
+ if (isEmpty()) {
+ return "";
}
-
- private String indent(int n, boolean removeBlanks) {
- Stream<String> stream = removeBlanks ? lines(Integer.MAX_VALUE, Integer.MAX_VALUE)
- : lines();
+ Stream<String> stream = lines();
if (n > 0) {
final String spaces = " ".repeat(n);
stream = stream.map(s -> spaces + s);
} else if (n == Integer.MIN_VALUE) {
stream = stream.map(s -> s.stripLeading());
@@ -2899,10 +2893,112 @@
return isLatin1() ? StringLatin1.lastIndexOfNonWhitespace(value)
: StringUTF16.lastIndexOfNonWhitespace(value);
}
/**
+ * Returns a string whose value is this string, with incidental white space
+ * removed from the beginning and end of every line.
+ * <p>
+ * Incidental 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 white space:
+ * <blockquote><pre>
+ * String html = """
+ * ..............<html>
+ * .............. <body>
+ * .............. <p>Hello, world</p>
+ * .............. </body>
+ * ..............</html>
+ * ..............""";
+ * </pre></blockquote>
+ * This method treats the incidental 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>
+ * |<html>
+ * | <body>
+ * | <p>Hello, world</p>
+ * | </body>
+ * |</html>
+ * </pre></blockquote>
+ * First, this string is conceptually separated into lines as if by
+ * {@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 {@link Character#isWhitespace(int) white space} characters are
+ * counted. The leading {@link Character#isWhitespace(int) white space}
+ * characters on the last line are are also counted even if blank.
+ * The <i>min</i> value is the smallest of these counts.
+ * <p>
+ * For each non-blank line, <i>min</i> leading white space characters are
+ * removed, and any trailing white space characters are removed.
+ * <p>
+ * Finally, the lines are joined with a line feed character {@code "\n"}
+ * (U+000A) into a single string and returned.
+ *
+ * @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 white space.
+ *
+ * @implNote
+ * This method treats all white space characters as having equal weight.
+ * 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 margins removed and line terminators normalized
+ *
+ * @see String#lines()
+ * @see String#isBlank()
+ * @see String#indent(int)
+ * @see Character#isWhitespace(int)
+ *
+ * @since 13
+ *
+ * @deprecated Preview feature associated with Text Blocks.
+ * Use at your own risk.
+ */
+ @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();
+ return firstNonWhitespace > lastNonWhitespace
+ ? "" : line.substring(Math.min(outdent, firstNonWhitespace), 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
* and produce an {@code R} result.
* <p>
* Any exception thrown by {@code f()} will be propagated to the
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