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performance refine for StringUtils.center
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2 files changed

+159
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‎src/main/java/org/apache/commons/lang3/StringUtils.java‎

Lines changed: 22 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -621,9 +621,11 @@ public static String center(String str, final int size, final char padChar) {
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if (pads <= 0) {
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return str;
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}
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str = leftPad(str, strLen + pads / 2, padChar);
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str = rightPad(str, size, padChar);
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return str;
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StringBuilder stringBuilder = new StringBuilder(size);
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repeat(stringBuilder, padChar, pads / 2);
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stringBuilder.append(str);
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repeat(stringBuilder, padChar, size - (strLen + pads / 2));
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return stringBuilder.toString();
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}
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/**
@@ -6253,6 +6255,23 @@ public static String repeat(final char ch, final int repeat) {
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return new String(buf);
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}
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/**
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* <p>Make the padding using the specified delimiter repeated
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* to a given length, and fill the result to a StringBuilder</p>
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*
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* This function works like {@code stringBuilder.append(repeat(ch,repeat))}, but runs faster.
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*
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* @param stringBuilder stringBuilder to fill
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* @param ch character to repeat
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* @param repeat number of times to repeat char, negative treated as zero
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* @see #repeat(char, int)
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*/
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static void repeat(StringBuilder stringBuilder, final char ch, final int repeat) {
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for (int i = repeat - 1; i >= 0; i--) {
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stringBuilder.append(ch);
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}
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}
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/**
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* <p>Repeat a String {@code repeat} times to form a
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* new String.</p>

‎src/test/java/org/apache/commons/lang3/StringUtilCenterTest.java‎

Lines changed: 137 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,137 @@
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/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.apache.commons.lang3;
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import org.openjdk.jmh.annotations.Benchmark;
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import org.openjdk.jmh.annotations.BenchmarkMode;
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import org.openjdk.jmh.annotations.Mode;
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import org.openjdk.jmh.annotations.OutputTimeUnit;
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import org.openjdk.jmh.annotations.Scope;
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import org.openjdk.jmh.annotations.State;
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import java.util.concurrent.TimeUnit;
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import static org.apache.commons.lang3.StringUtils.leftPad;
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import static org.apache.commons.lang3.StringUtils.repeat;
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import static org.apache.commons.lang3.StringUtils.rightPad;
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/**
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* Test to show whether using BitSet for removeAll() methods is faster than using HashSet.
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*/
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@BenchmarkMode(Mode.AverageTime)
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@OutputTimeUnit(TimeUnit.NANOSECONDS)
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@State(Scope.Thread)
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public class StringUtilCenterTest {
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@Benchmark
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public void test0Old() {
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centerOld("a", 20, 'a');
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}
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@Benchmark
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public void test0New() {
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centerNew("a", 20, 'a');
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}
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@Benchmark
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public void test1Old() {
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centerOld("a", 10000000, ' ');
53+
}
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@Benchmark
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public void test1New() {
57+
centerNew("a", 10000000, ' ');
58+
}
59+
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/**
61+
* <p>Centers a String in a larger String of size {@code size}.
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* Uses a supplied character as the value to pad the String with.</p>
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*
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* <p>If the size is less than the String length, the String is returned.
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* A {@code null} String returns {@code null}.
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* A negative size is treated as zero.</p>
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*
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* <pre>
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* StringUtils.center(null, *, *) = null
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* StringUtils.center("", 4, ' ') = " "
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* StringUtils.center("ab", -1, ' ') = "ab"
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* StringUtils.center("ab", 4, ' ') = " ab "
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* StringUtils.center("abcd", 2, ' ') = "abcd"
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* StringUtils.center("a", 4, ' ') = " a "
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* StringUtils.center("a", 4, 'y') = "yayy"
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* </pre>
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*
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* @param str the String to center, may be null
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* @param size the int size of new String, negative treated as zero
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* @param padChar the character to pad the new String with
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* @return centered String, {@code null} if null String input
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* @since 2.0
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*/
84+
public static String centerNew(String str, final int size, final char padChar) {
85+
if (str == null || size <= 0) {
86+
return str;
87+
}
88+
final int strLen = str.length();
89+
final int pads = size - strLen;
90+
if (pads <= 0) {
91+
return str;
92+
}
93+
StringBuilder stringBuilder = new StringBuilder(size);
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repeat(stringBuilder, padChar, pads / 2);
95+
stringBuilder.append(str);
96+
repeat(stringBuilder, padChar, size - (strLen + pads / 2));
97+
return stringBuilder.toString();
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}
99+
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/**
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* <p>Centers a String in a larger String of size {@code size}.
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* Uses a supplied character as the value to pad the String with.</p>
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*
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* <p>If the size is less than the String length, the String is returned.
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* A {@code null} String returns {@code null}.
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* A negative size is treated as zero.</p>
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*
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* <pre>
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* StringUtils.center(null, *, *) = null
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* StringUtils.center("", 4, ' ') = " "
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* StringUtils.center("ab", -1, ' ') = "ab"
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* StringUtils.center("ab", 4, ' ') = " ab "
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* StringUtils.center("abcd", 2, ' ') = "abcd"
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* StringUtils.center("a", 4, ' ') = " a "
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* StringUtils.center("a", 4, 'y') = "yayy"
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* </pre>
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*
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* @param str the String to center, may be null
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* @param size the int size of new String, negative treated as zero
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* @param padChar the character to pad the new String with
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* @return centered String, {@code null} if null String input
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* @since 2.0
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*/
124+
public static String centerOld(String str, final int size, final char padChar) {
125+
if (str == null || size <= 0) {
126+
return str;
127+
}
128+
final int strLen = str.length();
129+
final int pads = size - strLen;
130+
if (pads <= 0) {
131+
return str;
132+
}
133+
str = leftPad(str, strLen + pads / 2, padChar);
134+
str = rightPad(str, size, padChar);
135+
return str;
136+
}
137+
}

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