Adding "Filtering List using regex code" | BAEL-8736

core-java-modules/core-java-regex-3/java-list-regex-filter/pom.xml

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<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>
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>3.3.4</version>
+        <relativePath/>
+    </parent>
+
+    <groupId>org.example</groupId>
+    <artifactId>java-list-regex-filter</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <repositories>
+        <repository>
+            <id>central</id>
+            <name>Central Repository</name>
+            <url>https://repo1.maven.org/maven2/</url>
+        </repository>
+    </repositories>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <maven.compiler.source>17</maven.compiler.source>
+        <maven.compiler.target>17</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+</project>

core-java-modules/core-java-regex-3/java-list-regex-filter/src/main/java/com/baeldung/RegexFilterExample.java

@@ -0,0 +1,61 @@
+package com.baeldung;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
+public class RegexFilterExample {
+
+    public List<String> method1() {
+        List<String> fruits = List.of("apple", "banana", "cherry", "apricot", "avocado");
+
+        Pattern pattern = Pattern.compile("^a.*");
+
+        return fruits.stream()
+          .filter(pattern.asPredicate())
+          .toList();
+    }
+
+    public List<String> method2() {
+        List<String> list = List.of("123", "abc", "456def", "789", "xyz");
+
+        return list.stream()
+          .filter(str -> str.matches("\\d+"))
+          .toList();
+    }
+
+    public List<String> method3() {
+        List<String> numbers = List.of("one", "two", "three", "four", "five");
+        List<String> startWithTList = new ArrayList<>();
+
+        Pattern pattern = Pattern.compile("^t.*");
+
+        for (String item : numbers) {
+            Matcher matcher = pattern.matcher(item);
+            if (matcher.matches())
+                startWithTList.add(item);
+        }
+
+        return startWithTList;
+    }
+
+    public Map<Boolean, List<String>> method4() {
+        List<String> fruits = List.of("apple", "banana", "apricot", "berry");
+
+        Pattern pattern = Pattern.compile("^a.*");
+
+        return fruits.stream()
+          .collect(Collectors.partitioningBy(pattern.asPredicate()));
+    }
+
+    public static void main(String[] args) {
+        RegexFilterExample regexFilterExample = new RegexFilterExample();
+        regexFilterExample.method1();
+        regexFilterExample.method2();
+        regexFilterExample.method3();
+        regexFilterExample.method4();
+    }
+}

core-java-modules/core-java-regex-3/java-list-regex-filter/src/test/java/com/baeldung/RegexFilterExampleUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung;
+
+import java.util.List;
+import java.util.Map;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class RegexFilterExampleUnitTest {
+
+    RegexFilterExample regexFilterExample = new RegexFilterExample();
+
+    @Test
+    void whenMethod1Called_thenReturnElementsStartingWithA() {
+        List<String> newList = regexFilterExample.method1();
+        Assertions.assertEquals(List.of("apple", "apricot", "avocado"), newList);
+    }
+
+    @Test
+    void whenMethod2Called_thenReturnElementsContainingDig() {
+        List<String> newList = regexFilterExample.method2();
+        Assertions.assertEquals(List.of("123", "789"), newList);
+    }
+
+    @Test
+    void whenMethod1Called_thenReturnElementsStartingWithT3() {
+        List<String> newList = regexFilterExample.method3();
+        Assertions.assertEquals(List.of("two", "three"), newList);
+    }
+
+    @Test
+    void whenMethod1Called_thenReturnElementsStartingWithA4() {
+        Map<Boolean, List<String>> newList = regexFilterExample.method4();
+        Assertions.assertEquals(List.of("apple", "apricot"), newList.get(true));
+        Assertions.assertEquals(List.of("banana", "berry"), newList.get(false));
+    }
+}