8223775: String::stripIndent (Preview)
Reviewed-by: abuckley, vromero, jlahoda, bchristi, rriggs, smarks
--- a/src/java.base/share/classes/java/lang/String.java Thu Jun 06 08:11:25 2019 -0700
+++ b/src/java.base/share/classes/java/lang/String.java Thu Jun 06 12:24:44 2019 -0300
@@ -36,6 +36,7 @@
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 @@
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 @@
* @since 11
*/
public Stream<String> lines() {
- return lines(0, 0);
+ return isLatin1() ? StringLatin1.lines(value) : StringUTF16.lines(value);
}
/**
@@ -2873,12 +2869,10 @@
* @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);
@@ -2901,6 +2895,123 @@
}
/**
+ * 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 = """
+ * ..............<html>
+ * .............. <body>
+ * .............. <p>Hello, world</p>
+ * .............. </body>
+ * ..............</html>
+ * ..............""";
+ * </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>
+ * |<html>
+ * | <body>
+ * | <p>Hello, world</p>
+ * | </body>
+ * |</html>
+ * </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
* and produce an {@code R} result.
--- a/src/java.base/share/classes/java/lang/StringLatin1.java Thu Jun 06 08:11:25 2019 -0700
+++ b/src/java.base/share/classes/java/lang/StringLatin1.java Thu Jun 06 12:24:44 2019 -0300
@@ -732,76 +732,10 @@
static LinesSpliterator spliterator(byte[] value) {
return new LinesSpliterator(value, 0, value.length);
}
-
- static LinesSpliterator spliterator(byte[] value, int leading, int trailing) {
- int length = value.length;
- int left = 0;
- int index;
- for (int l = 0; l < leading; l++) {
- index = skipBlankForward(value, left, length);
- if (index == left) {
- break;
- }
- left = index;
- }
- int right = length;
- for (int t = 0; t < trailing; t++) {
- index = skipBlankBackward(value, left, right);
- if (index == right) {
- break;
- }
- right = index;
- }
- return new LinesSpliterator(value, left, right - left);
- }
-
- private static int skipBlankForward(byte[] value, int start, int length) {
- int index = start;
- while (index < length) {
- char ch = getChar(value, index++);
- if (ch == '\n') {
- return index;
- }
- if (ch == '\r') {
- if (index < length && getChar(value, index) == '\n') {
- return index + 1;
- }
- return index;
- }
- if (ch != ' ' && ch != '\t' && !Character.isWhitespace(ch)) {
- return start;
- }
- }
- return length;
- }
-
- private static int skipBlankBackward(byte[] value, int start, int fence) {
- int index = fence;
- if (start < index && getChar(value, index - 1) == '\n') {
- index--;
- }
- if (start < index && getChar(value, index - 1) == '\r') {
- index--;
- }
- while (start < index) {
- char ch = getChar(value, --index);
- if (ch == '\r' || ch == '\n') {
- return index + 1;
- }
- if (ch != ' ' && ch != '\t' && !Character.isWhitespace(ch)) {
- return fence;
- }
- }
- return start;
- }
}
- static Stream<String> lines(byte[] value, int leading, int trailing) {
- if (leading == 0 && trailing == 0) {
- return StreamSupport.stream(LinesSpliterator.spliterator(value), false);
- } else {
- return StreamSupport.stream(LinesSpliterator.spliterator(value, leading, trailing), false);
- }
+ static Stream<String> lines(byte[] value) {
+ return StreamSupport.stream(LinesSpliterator.spliterator(value), false);
}
public static void putChar(byte[] val, int index, int c) {
--- a/src/java.base/share/classes/java/lang/StringUTF16.java Thu Jun 06 08:11:25 2019 -0700
+++ b/src/java.base/share/classes/java/lang/StringUTF16.java Thu Jun 06 12:24:44 2019 -0300
@@ -1119,76 +1119,10 @@
static LinesSpliterator spliterator(byte[] value) {
return new LinesSpliterator(value, 0, value.length >>> 1);
}
-
- static LinesSpliterator spliterator(byte[] value, int leading, int trailing) {
- int length = value.length >>> 1;
- int left = 0;
- int index;
- for (int l = 0; l < leading; l++) {
- index = skipBlankForward(value, left, length);
- if (index == left) {
- break;
- }
- left = index;
- }
- int right = length;
- for (int t = 0; t < trailing; t++) {
- index = skipBlankBackward(value, left, right);
- if (index == right) {
- break;
- }
- right = index;
- }
- return new LinesSpliterator(value, left, right - left);
- }
-
- private static int skipBlankForward(byte[] value, int start, int length) {
- int index = start;
- while (index < length) {
- char ch = getChar(value, index++);
- if (ch == '\n') {
- return index;
- }
- if (ch == '\r') {
- if (index < length && getChar(value, index) == '\n') {
- return index + 1;
- }
- return index;
- }
- if (ch != ' ' && ch != '\t' && !Character.isWhitespace(ch)) {
- return start;
- }
- }
- return length;
- }
-
- private static int skipBlankBackward(byte[] value, int start, int fence) {
- int index = fence;
- if (start < index && getChar(value, index - 1) == '\n') {
- index--;
- }
- if (start < index && getChar(value, index - 1) == '\r') {
- index--;
- }
- while (start < index) {
- char ch = getChar(value, --index);
- if (ch == '\r' || ch == '\n') {
- return index + 1;
- }
- if (ch != ' ' && ch != '\t' && !Character.isWhitespace(ch)) {
- return fence;
- }
- }
- return start;
- }
}
- static Stream<String> lines(byte[] value, int leading, int trailing) {
- if (leading == 0 && trailing == 0) {
- return StreamSupport.stream(LinesSpliterator.spliterator(value), false);
- } else {
- return StreamSupport.stream(LinesSpliterator.spliterator(value, leading, trailing), false);
- }
+ static Stream<String> lines(byte[] value) {
+ return StreamSupport.stream(LinesSpliterator.spliterator(value), false);
}
private static void putChars(byte[] val, int index, char[] str, int off, int end) {
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/lang/String/StripIndent.java Thu Jun 06 12:24:44 2019 -0300
@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8223775
+ * @summary This exercises String#stripIndent patterns and limits.
+ * @run main StripIndent
+ */
+
+public class StripIndent {
+ public static void main(String... arg) {
+ test1();
+ }
+
+ /*
+ * Case combinations.
+ */
+ static void test1() {
+ verify("", "");
+ verify("abc", "abc");
+ verify(" abc", "abc");
+ verify("abc ", "abc");
+ verify(" abc\n def\n ", "abc\ndef\n");
+ verify(" abc\n def\n", " abc\n def\n");
+ verify(" abc\n def", "abc\ndef");
+ verify(" abc\n def\n ", "abc\n def\n");
+ }
+
+ static void verify(String a, String b) {
+ if (!a.stripIndent().equals(b)) {
+ System.err.format("\"%s\" not equal \"%s\"%n", a, b);
+ throw new RuntimeException();
+ }
+ }
+}
+
+