这是indexloc提供的服务，不要输入任何密码
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[count-substr] count seq in a string #18814

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Merged
merged 2 commits into from
Sep 22, 2025
Merged

[count-substr] count seq in a string #18814

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06f83d6
[count-substr] count seq in a string
sk1418 Sep 17, 2025
55af1ac
[count-substr] move to -6 module
sk1418 Sep 19, 2025
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27 changes: 27 additions & 0 deletions core-java-modules/core-java-string-algorithms-6/pom.xml
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@@ -0,0 +1,27 @@
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<artifactId>core-java-string-algorithms-6</artifactId>
<packaging>jar</packaging>
<name>core-java-string-algorithms-6</name>

<parent>
<groupId>com.baeldung.core-java-modules</groupId>
<artifactId>core-java-modules</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>

<dependencies>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>${common-lang3.version}</version>
</dependency>
</dependencies>

<properties>
<common-lang3.version>3.18.0</common-lang3.version>
</properties>

</project>
78 changes: 78 additions & 0 deletions ...tring-algorithms-6/src/test/java/com/baeldung/countseq/CountSequenceInStringUnitTest.java
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package com.baeldung.countseq;

import static org.junit.jupiter.api.Assertions.assertEquals;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.lang3.StringUtils;
import org.junit.jupiter.api.Test;

public class CountSequenceInStringUnitTest {

private final static String INPUT = "This is a test string. This test is for testing the count of a sequence in a string. This string has three sentences.";

int countSeqByIndexOf(String input, String seq) {
int count = 0;
int index = input.indexOf(seq);
while (index != -1) {
count++;
index = input.indexOf(seq, index + seq.length());
}
return count;
}

@Test
void whenUsingIndexOf_thenCorrect() {
assertEquals(3, countSeqByIndexOf(INPUT, "string"));
assertEquals(2, countSeqByIndexOf(INPUT, "string."));
}

int countSeqByRegexFind(String input, String seq) {
// Alternative: Pattern pattern = Pattern.compile(seq, Pattern.LITERAL);
Matcher matcher = Pattern.compile(Pattern.quote(seq))
.matcher(input);
int count = 0;
while (matcher.find()) {
count++;
}
return count;
}

@Test
void whenUsingRegexFind_thenCorrect() {
assertEquals(3, countSeqByRegexFind(INPUT, "string"));
assertEquals(2, countSeqByRegexFind(INPUT, "string."));
}

int countSeqByRegexSplit(String input, String seq) {
Pattern pattern = Pattern.compile(seq, Pattern.LITERAL);
return pattern.split(input, -1).length - 1;
}

@Test
void whenUsingRegexSplit_thenCorrect() {
assertEquals(3, countSeqByRegexSplit(INPUT, "string"));
assertEquals(2, countSeqByRegexSplit(INPUT, "string."));
}

int countSeqByStream(String input, String seq) {
long count = Pattern.compile(Pattern.quote(seq))
.matcher(input)
.results()
.count();
return Math.toIntExact(count);
}

@Test
void whenUsingStream_thenCorrect() {
assertEquals(3, countSeqByStream(INPUT, "string"));
assertEquals(2, countSeqByStream(INPUT, "string."));
}

@Test
void whenUsingApacheCommonsLangCountMatches_thenCorrect() {
assertEquals(3, StringUtils.countMatches(INPUT, "string"));
assertEquals(2, StringUtils.countMatches(INPUT, "string."));
}
}
1 change: 1 addition & 0 deletions core-java-modules/pom.xml
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Expand Up @@ -242,6 +242,7 @@
<module>core-java-string-algorithms-3</module>
<module>core-java-string-algorithms-4</module>
<module>core-java-string-algorithms-5</module>
<module>core-java-string-algorithms-6</module>
<module>core-java-string-apis</module>
<module>core-java-string-apis-2</module>
<module>core-java-swing</module>
Expand Down