8197594: String#repeat
Reviewed-by: smarks, psandoz, plevart, rriggs, redestad
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@ -2963,6 +2963,56 @@ public final class String
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*/
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public native String intern();
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/**
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* Returns a string whose value is the concatenation of this
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* string repeated {@code count} times.
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* <p>
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* If this string is empty or count is zero then the empty
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* string is returned.
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*
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* @param count number of times to repeat
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*
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* @return A string composed of this string repeated
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* {@code count} times or the empty string if this
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* string is empty or count is zero
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*
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* @throws IllegalArgumentException if the {@code count} is
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* negative.
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*
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* @since 11
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*/
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public String repeat(int count) {
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if (count < 0) {
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throw new IllegalArgumentException("count is negative: " + count);
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}
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if (count == 1) {
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return this;
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}
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final int len = value.length;
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if (len == 0 || count == 0) {
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return "";
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}
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if (len == 1) {
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final byte[] single = new byte[count];
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Arrays.fill(single, value[0]);
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return new String(single, coder);
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}
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if (Integer.MAX_VALUE / count < len) {
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throw new OutOfMemoryError("Repeating " + len + " bytes String " + count +
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" times will produce a String exceeding maximum size.");
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}
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final int limit = len * count;
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final byte[] multiple = new byte[limit];
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System.arraycopy(value, 0, multiple, 0, len);
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int copied = len;
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for (int next = copied << 1; next < limit && 0 < next; next = next << 1) {
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System.arraycopy(multiple, 0, multiple, copied, copied);
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copied = next;
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}
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System.arraycopy(multiple, 0, multiple, copied, limit - copied);
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return new String(multiple, coder);
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}
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////////////////////////////////////////////////////////////////
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/**
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133
test/jdk/java/lang/String/StringRepeat.java
Normal file
133
test/jdk/java/lang/String/StringRepeat.java
Normal file
@ -0,0 +1,133 @@
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/*
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* Copyright (c) 2018, 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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* @summary This exercises String#repeat patterns and limits.
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* @run main/othervm -Xmx4G StringRepeat
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*/
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import java.nio.CharBuffer;
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public class StringRepeat {
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public static void main(String... arg) {
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test1();
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test2();
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}
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/*
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* Varitions of repeat count.
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*/
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static int[] REPEATS = {
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
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32, 64, 128, 256, 512, 1024, 64 * 1024, 1024 * 1024,
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16 * 1024 * 1024
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};
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/*
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* Varitions of Strings.
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*/
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static String[] STRINGS = new String[] {
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"", "\0", " ", "a", "$", "\u2022",
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"ab", "abc", "abcd", "abcde",
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"The quick brown fox jumps over the lazy dog."
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};
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/*
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* Repeat String function tests.
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*/
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static void test1() {
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for (int repeat : REPEATS) {
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for (String string : STRINGS) {
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long limit = (long)string.length() * (long)repeat;
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if ((long)(Integer.MAX_VALUE >> 1) <= limit) {
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break;
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}
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verify(string.repeat(repeat), string, repeat);
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}
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}
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}
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/*
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* Repeat String exception tests.
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*/
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static void test2() {
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try {
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"abc".repeat(-1);
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throw new RuntimeException("No exception for negative repeat count");
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} catch (IllegalArgumentException ex) {
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// Correct
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}
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try {
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"abc".repeat(Integer.MAX_VALUE - 1);
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throw new RuntimeException("No exception for large repeat count");
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} catch (OutOfMemoryError ex) {
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// Correct
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}
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}
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static String truncate(String string) {
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if (string.length() < 80) {
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return string;
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}
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return string.substring(0, 80) + "...";
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}
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/*
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* Verify string repeat patterns.
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*/
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static void verify(String result, String string, int repeat) {
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if (string.isEmpty() || repeat == 0) {
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if (!result.isEmpty()) {
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System.err.format("\"%s\".repeat(%d)%n", truncate(string), repeat);
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System.err.format("Result \"%s\"%n", truncate(result));
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System.err.format("Result expected to be empty, found string of length %d%n", result.length());
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throw new RuntimeException();
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}
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} else {
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int expected = 0;
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int count = 0;
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for (int offset = result.indexOf(string, expected);
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0 <= offset;
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offset = result.indexOf(string, expected)) {
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count++;
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if (offset != expected) {
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System.err.format("\"%s\".repeat(%d)%n", truncate(string), repeat);
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System.err.format("Result \"%s\"%n", truncate(result));
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System.err.format("Repeat expected at %d, found at = %d%n", expected, offset);
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throw new RuntimeException();
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}
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expected += string.length();
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}
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if (count != repeat) {
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System.err.format("\"%s\".repeat(%d)%n", truncate(string), repeat);
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System.err.format("Result \"%s\"%n", truncate(result));
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System.err.format("Repeat count expected to be %d, found %d%n", repeat, count);
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throw new RuntimeException();
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}
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}
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}
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}
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