Improve performance of StringUtils.isMixedCase() (#1096)

* improve performance of isMixedCase

The changes optimize the mixed-case detecting function in StringUtils.java by reducing redundant character property checks. The loop will now return early when both uppercase and lowercase are present, preventing further unnecessary operations. It also introduces a local variable to store the character being checked, reducing the number of method calls to get the character. The end return statement is also simplified to return false, as the true condition has already been covered inside the loop.

* add test to prove better performance

* Add Apache license header to StringUtilsIsMixedCaseTest.java file

* Fix Checkstyle issues

---------

Co-authored-by: Gary Gregory <garydgregory@users.noreply.github.com>
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hduelme 2023-08-16 19:24:27 +02:00 committed by GitHub
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commit 19fa964de7
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2 changed files with 109 additions and 6 deletions

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@ -3628,16 +3628,17 @@ public class StringUtils {
boolean containsLowercase = false;
final int sz = cs.length();
for (int i = 0; i < sz; i++) {
char nowChar = cs.charAt(i);
if (Character.isUpperCase(nowChar)) {
containsUppercase = true;
} else if (Character.isLowerCase(nowChar)) {
containsLowercase = true;
}
if (containsUppercase && containsLowercase) {
return true;
}
if (Character.isUpperCase(cs.charAt(i))) {
containsUppercase = true;
} else if (Character.isLowerCase(cs.charAt(i))) {
containsLowercase = true;
}
}
return containsUppercase && containsLowercase;
return false;
}
/**

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@ -0,0 +1,102 @@
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.lang3;
import java.util.concurrent.TimeUnit;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.Warmup;
/**
* Test to show the better performance of the new implementation of isMixedCase
*/
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@State(Scope.Thread)
@Warmup(iterations = 5, time = 10)
public class StringUtilsIsMixedCaseTest {
public static final String LOWER_CASE_LETTERS = "abcdefghijklmnopqrstuvwxyz";
public static final String END_MATCH = "at the enD";
public static final String Middle_MATCH = "at tHe Mid";
public static final String EARLY_MATCH = "At tHe beginning";
@Benchmark
public boolean newIsMixedCaseNoneMatch() {
return StringUtils.isMixedCase(LOWER_CASE_LETTERS);
}
@Benchmark
public boolean oldIsMixedCaseNoneMatch() {
return oldIsMixedCase(LOWER_CASE_LETTERS);
}
@Benchmark
public boolean newIsMixedCaseEndMatch() {
return StringUtils.isMixedCase(END_MATCH);
}
@Benchmark
public boolean oldIsMixedCaseEndMatch() {
return oldIsMixedCase(END_MATCH);
}
@Benchmark
public boolean newIsMixedCaseMiddleMatch() {
return StringUtils.isMixedCase(Middle_MATCH);
}
@Benchmark
public boolean oldIsMixedCaseMiddleMatch() {
return oldIsMixedCase(Middle_MATCH);
}
@Benchmark
public boolean newIsMixedCaseBeginningMatch() {
return StringUtils.isMixedCase(EARLY_MATCH);
}
@Benchmark
public boolean oldIsMixedCaseBeginningMatch() {
return oldIsMixedCase(EARLY_MATCH);
}
public static boolean oldIsMixedCase(final CharSequence cs) {
if (StringUtils.isEmpty(cs) || cs.length() == 1) {
return false;
}
boolean containsUppercase = false;
boolean containsLowercase = false;
final int sz = cs.length();
for (int i = 0; i < sz; i++) {
if (containsUppercase && containsLowercase) {
return true;
}
if (Character.isUpperCase(cs.charAt(i))) {
containsUppercase = true;
} else if (Character.isLowerCase(cs.charAt(i))) {
containsLowercase = true;
}
}
return containsUppercase && containsLowercase;
}
}