+ * If count or length is zero then the empty string is returned. + *
+ * This method may be used to create space padding for + * formatting text or zero padding for formatting numbers. + * @param count number of times to repeat + * @return A string composed of this string repeated + * {@code count} times or the empty string if count + * or length is zero. + * @throws IllegalArgumentException if the {@code count} is + * negative. + */ + public String repeat(int count) { + if (count < 0) { + throw new IllegalArgumentException("count is negative, " + count); + } + if (count == 1) { + return this; + } + final int len = value.length; + if (len == 0 || count == 0) { + return ""; + } + if (len == 1) { + final byte[] single = new byte[count]; + Arrays.fill(single, value[0]); + return new String(single, coder); + } + if (Integer.MAX_VALUE / count < len) { + throw new OutOfMemoryError(); + } + final int limit = len * count; + final byte[] multiple = new byte[limit]; + System.arraycopy(value, 0, multiple, 0, len); + int copied = len; + for (int next = copied << 1; next < limit && 0 < next; next = next << 1) { + System.arraycopy(multiple, 0, multiple, copied, copied); + copied = next; + } + System.arraycopy(multiple, 0, multiple, copied, limit - copied); + return new String(multiple, coder); + } + //////////////////////////////////////////////////////////////// /** diff --git a/test/jdk/java/lang/String/StringRepeat.java b/test/jdk/java/lang/String/StringRepeat.java new file mode 100644 --- /dev/null +++ b/test/jdk/java/lang/String/StringRepeat.java @@ -0,0 +1,133 @@ +/* + * Copyright (c) 2018, 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 + * @summary This exercises String#repeat patterns and limits. + * @run main/othervm -Xmx4G StringRepeat + */ + +import java.nio.CharBuffer; + +public class StringRepeat { + public static void main(String... arg) { + test1(); + test2(); + } + + /* + * Varitions of repeat count. + */ + static int[] REPEATS = { + 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, + 32, 64, 128, 256, 512, 1024, 64 * 1024, 1024 * 1024, + 16 * 1024 * 1024 + }; + + /* + * Varitions of Strings. + */ + static String[] STRINGS = new String[] { + "", "\0", " ", "a", "$", "\u2022", + "ab", "abc", "abcd", "abcde", + "The quick brown fox jumps over the lazy dog." + }; + + /* + * Repeat String function tests. + */ + static void test1() { + for (int repeat : REPEATS) { + for (String string : STRINGS) { + long limit = (long)string.length() * (long)repeat; + + if ((long)(Integer.MAX_VALUE >> 1) <= limit) { + break; + } + + VERIFY(string.repeat(repeat), string, repeat); + } + } + } + + /* + * Repeat String exception tests. + */ + static void test2() { + try { + "abc".repeat(-1); + throw new RuntimeException("No exception for negative repeat count"); + } catch (IllegalArgumentException ex) { + // Correct + } + + try { + "abc".repeat(Integer.MAX_VALUE - 1); + throw new RuntimeException("No exception for large repeat count"); + } catch (OutOfMemoryError ex) { + // Correct + } + } + + static String truncate(String string) { + if (string.length() < 80) { + return string; + } + return string.substring(0, 80) + "..."; + } + + /* + * Verify string repeat patterns. + */ + static void VERIFY(String result, String string, int repeat) { + if (string.isEmpty() || repeat == 0) { + if (!result.isEmpty()) { + System.err.format("\"%s\".repeat(%d)%n", truncate(string), repeat); + System.err.format("Result \"%s\"%n", truncate(result)); + System.err.format("Result expected to be empty, found string of length %d%n", result.length()); + throw new RuntimeException(); + } + } else { + int expected = 0; + int count = 0; + for (int offset = result.indexOf(string, expected); + 0 <= offset; + offset = result.indexOf(string, expected)) { + count++; + if (offset != expected) { + System.err.format("\"%s\".repeat(%d)%n", truncate(string), repeat); + System.err.format("Result \"%s\"%n", truncate(result)); + System.err.format("Repeat expected at %d, found at = %d%n", expected, offset); + throw new RuntimeException(); + } + expected += string.length(); + } + if (count != repeat) { + System.err.format("\"%s\".repeat(%d)%n", truncate(string), repeat); + System.err.format("Result \"%s\"%n", truncate(result)); + System.err.format("Repeat count expected to be %d, found %d%n", repeat, count); + throw new RuntimeException(); + } + } + } +}