8223775: String::stripIndent (Preview)
Reviewed-by: abuckley, vromero, jlahoda, bchristi, rriggs, smarks
This commit is contained in:
Jim Laskey
parent
618afc3fa2
commit
0777a86d68
@ -36,6 +36,7 @@ import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.Comparator;
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import java.util.Formatter;
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import java.util.List;
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import java.util.Locale;
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import java.util.Objects;
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import java.util.Optional;
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@ -2797,11 +2798,6 @@ public final class String
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return indexOfNonWhitespace() == length();
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}
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private Stream<String> lines(int maxLeading, int maxTrailing) {
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return isLatin1() ? StringLatin1.lines(value, maxLeading, maxTrailing)
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: StringUTF16.lines(value, maxLeading, maxTrailing);
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}
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/**
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* Returns a stream of lines extracted from this string,
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* separated by line terminators.
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@ -2833,7 +2829,7 @@ public final class String
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* @since 11
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*/
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public Stream<String> lines() {
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return lines(0, 0);
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return isLatin1() ? StringLatin1.lines(value) : StringUTF16.lines(value);
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}
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/**
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@ -2873,12 +2869,10 @@ public final class String
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* @since 12
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*/
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public String indent(int n) {
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return isEmpty() ? "" : indent(n, false);
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}
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private String indent(int n, boolean removeBlanks) {
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Stream<String> stream = removeBlanks ? lines(Integer.MAX_VALUE, Integer.MAX_VALUE)
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: lines();
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if (isEmpty()) {
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return "";
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}
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Stream<String> stream = lines();
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if (n > 0) {
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final String spaces = " ".repeat(n);
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stream = stream.map(s -> spaces + s);
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@ -2900,6 +2894,123 @@ public final class String
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: StringUTF16.lastIndexOfNonWhitespace(value);
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}
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/**
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* Returns a string whose value is this string, with incidental
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* {@linkplain Character#isWhitespace(int) white space} removed from
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* the beginning and end of every line.
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* <p>
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* Incidental {@linkplain Character#isWhitespace(int) white space}
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* is often present in a text block to align the content with the opening
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* delimiter. For example, in the following code, dots represent incidental
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* {@linkplain Character#isWhitespace(int) white space}:
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* <blockquote><pre>
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* String html = """
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* ..............<html>
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* .............. <body>
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* .............. <p>Hello, world</p>
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* .............. </body>
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* ..............</html>
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* ..............""";
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* </pre></blockquote>
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* This method treats the incidental
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* {@linkplain Character#isWhitespace(int) white space} as indentation to be
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* stripped, producing a string that preserves the relative indentation of
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* the content. Using | to visualize the start of each line of the string:
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* <blockquote><pre>
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* |<html>
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* | <body>
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* | <p>Hello, world</p>
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* | </body>
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* |</html>
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* </pre></blockquote>
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* First, the individual lines of this string are extracted as if by using
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* {@link String#lines()}.
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* <p>
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* Then, the <i>minimum indentation</i> (min) is determined as follows.
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* For each non-blank line (as defined by {@link String#isBlank()}), the
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* leading {@linkplain Character#isWhitespace(int) white space} characters are
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* counted. The leading {@linkplain Character#isWhitespace(int) white space}
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* characters on the last line are also counted even if
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* {@linkplain String#isBlank() blank}. The <i>min</i> value is the smallest
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* of these counts.
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* <p>
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* For each {@linkplain String#isBlank() non-blank} line, <i>min</i> leading
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* {@linkplain Character#isWhitespace(int) white space} characters are removed,
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* and any trailing {@linkplain Character#isWhitespace(int) white space}
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* characters are removed. {@linkplain String#isBlank() Blank} lines are
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* replaced with the empty string.
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*
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* <p>
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* Finally, the lines are joined into a new string, using the LF character
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* {@code "\n"} (U+000A) to separate lines.
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*
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* @apiNote
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* This method's primary purpose is to shift a block of lines as far as
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* possible to the left, while preserving relative indentation. Lines
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* that were indented the least will thus have no leading
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* {@linkplain Character#isWhitespace(int) white space}.
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* The line count of the result will be the same as line count of this
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* string.
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* If this string ends with a line terminator then the result will end
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* with a line terminator.
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*
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* @implNote
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* This method treats all {@linkplain Character#isWhitespace(int) white space}
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* characters as having equal width. As long as the indentation on every
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* line is consistently composed of the same character sequences, then the
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* result will be as described above.
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*
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* @return string with incidental indentation removed and line
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* terminators normalized
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*
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* @see String#lines()
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* @see String#isBlank()
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* @see String#indent(int)
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* @see Character#isWhitespace(int)
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*
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* @since 13
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*
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* @deprecated This method is associated with text blocks, a preview language feature.
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* Text blocks and/or this method may be changed or removed in a future release.
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*/
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@Deprecated(forRemoval=true, since="13")
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public String stripIndent() {
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int length = length();
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if (length == 0) {
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return "";
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}
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char lastChar = charAt(length - 1);
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boolean optOut = lastChar == '\n' || lastChar == '\r';
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List<String> lines = lines().collect(Collectors.toList());
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final int outdent = optOut ? 0 : outdent(lines);
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return lines.stream()
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.map(line -> {
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int firstNonWhitespace = line.indexOfNonWhitespace();
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int lastNonWhitespace = line.lastIndexOfNonWhitespace();
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int incidentalWhitespace = Math.min(outdent, firstNonWhitespace);
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return firstNonWhitespace > lastNonWhitespace
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? "" : line.substring(incidentalWhitespace, lastNonWhitespace);
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})
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.collect(Collectors.joining("\n", "", optOut ? "\n" : ""));
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}
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private static int outdent(List<String> lines) {
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// Note: outdent is guaranteed to be zero or positive number.
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// If there isn't a non-blank line then the last must be blank
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int outdent = Integer.MAX_VALUE;
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for (String line : lines) {
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int leadingWhitespace = line.indexOfNonWhitespace();
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if (leadingWhitespace != line.length()) {
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outdent = Integer.min(outdent, leadingWhitespace);
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}
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}
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String lastLine = lines.get(lines.size() - 1);
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if (lastLine.isBlank()) {
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outdent = Integer.min(outdent, lastLine.length());
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}
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return outdent;
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}
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/**
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* This method allows the application of a function to {@code this}
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* string. The function should expect a single String argument
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@ -732,76 +732,10 @@ final class StringLatin1 {
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static LinesSpliterator spliterator(byte[] value) {
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return new LinesSpliterator(value, 0, value.length);
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}
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static LinesSpliterator spliterator(byte[] value, int leading, int trailing) {
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int length = value.length;
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int left = 0;
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int index;
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for (int l = 0; l < leading; l++) {
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index = skipBlankForward(value, left, length);
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if (index == left) {
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break;
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}
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left = index;
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}
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int right = length;
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for (int t = 0; t < trailing; t++) {
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index = skipBlankBackward(value, left, right);
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if (index == right) {
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break;
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}
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right = index;
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}
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return new LinesSpliterator(value, left, right - left);
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}
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private static int skipBlankForward(byte[] value, int start, int length) {
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int index = start;
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while (index < length) {
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char ch = getChar(value, index++);
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if (ch == '\n') {
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return index;
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}
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if (ch == '\r') {
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if (index < length && getChar(value, index) == '\n') {
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return index + 1;
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}
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return index;
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}
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if (ch != ' ' && ch != '\t' && !Character.isWhitespace(ch)) {
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return start;
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}
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}
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return length;
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}
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private static int skipBlankBackward(byte[] value, int start, int fence) {
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int index = fence;
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if (start < index && getChar(value, index - 1) == '\n') {
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index--;
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}
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if (start < index && getChar(value, index - 1) == '\r') {
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index--;
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}
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while (start < index) {
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char ch = getChar(value, --index);
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if (ch == '\r' || ch == '\n') {
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return index + 1;
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}
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if (ch != ' ' && ch != '\t' && !Character.isWhitespace(ch)) {
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return fence;
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}
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}
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return start;
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}
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}
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static Stream<String> lines(byte[] value, int leading, int trailing) {
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if (leading == 0 && trailing == 0) {
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return StreamSupport.stream(LinesSpliterator.spliterator(value), false);
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} else {
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return StreamSupport.stream(LinesSpliterator.spliterator(value, leading, trailing), false);
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}
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static Stream<String> lines(byte[] value) {
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return StreamSupport.stream(LinesSpliterator.spliterator(value), false);
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}
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public static void putChar(byte[] val, int index, int c) {
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@ -1119,76 +1119,10 @@ final class StringUTF16 {
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static LinesSpliterator spliterator(byte[] value) {
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return new LinesSpliterator(value, 0, value.length >>> 1);
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}
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static LinesSpliterator spliterator(byte[] value, int leading, int trailing) {
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int length = value.length >>> 1;
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int left = 0;
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int index;
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for (int l = 0; l < leading; l++) {
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index = skipBlankForward(value, left, length);
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if (index == left) {
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break;
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}
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left = index;
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}
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int right = length;
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for (int t = 0; t < trailing; t++) {
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index = skipBlankBackward(value, left, right);
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if (index == right) {
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break;
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}
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right = index;
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}
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return new LinesSpliterator(value, left, right - left);
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}
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private static int skipBlankForward(byte[] value, int start, int length) {
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int index = start;
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while (index < length) {
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char ch = getChar(value, index++);
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if (ch == '\n') {
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return index;
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}
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if (ch == '\r') {
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if (index < length && getChar(value, index) == '\n') {
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return index + 1;
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}
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return index;
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}
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if (ch != ' ' && ch != '\t' && !Character.isWhitespace(ch)) {
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return start;
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}
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}
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return length;
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}
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private static int skipBlankBackward(byte[] value, int start, int fence) {
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int index = fence;
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if (start < index && getChar(value, index - 1) == '\n') {
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index--;
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}
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if (start < index && getChar(value, index - 1) == '\r') {
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index--;
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}
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while (start < index) {
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char ch = getChar(value, --index);
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if (ch == '\r' || ch == '\n') {
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return index + 1;
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}
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if (ch != ' ' && ch != '\t' && !Character.isWhitespace(ch)) {
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return fence;
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}
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}
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return start;
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}
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}
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static Stream<String> lines(byte[] value, int leading, int trailing) {
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if (leading == 0 && trailing == 0) {
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return StreamSupport.stream(LinesSpliterator.spliterator(value), false);
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} else {
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return StreamSupport.stream(LinesSpliterator.spliterator(value, leading, trailing), false);
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}
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static Stream<String> lines(byte[] value) {
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return StreamSupport.stream(LinesSpliterator.spliterator(value), false);
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}
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private static void putChars(byte[] val, int index, char[] str, int off, int end) {
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58
test/jdk/java/lang/String/StripIndent.java
Normal file
58
test/jdk/java/lang/String/StripIndent.java
Normal file
@ -0,0 +1,58 @@
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/*
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* Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* @test
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* @bug 8223775
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* @summary This exercises String#stripIndent patterns and limits.
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* @run main StripIndent
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*/
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public class StripIndent {
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public static void main(String... arg) {
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test1();
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}
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/*
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* Case combinations.
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*/
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static void test1() {
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verify("", "");
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verify("abc", "abc");
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verify(" abc", "abc");
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verify("abc ", "abc");
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verify(" abc\n def\n ", "abc\ndef\n");
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verify(" abc\n def\n", " abc\n def\n");
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verify(" abc\n def", "abc\ndef");
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verify(" abc\n def\n ", "abc\n def\n");
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}
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static void verify(String a, String b) {
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if (!a.stripIndent().equals(b)) {
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System.err.format("\"%s\" not equal \"%s\"%n", a, b);
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throw new RuntimeException();
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}
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}
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}
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