This PR is related to BAEL-7427 (#16028)

* This commit is related to BAEL-7427

This commit aims to add a Main class.

* This commit is related to BAEL-7427

This commit aims to add a myFile.gz file to the resources folder.

* This commit is related to BAEL-7427

This commit aims to add a test class "ReadingGZIPUsingGZIPInputStreamUnitTest".

* This commit is related to BAEL-7427

This commit aims to add a myFile.gz file to the resources folder.

* Update Main.java

* Update ReadingGZIPUsingGZIPInputStreamUnitTest.java

* Update Main.java

* Update ReadingGZIPUsingGZIPInputStreamUnitTest.java

* Update ReadingGZIPUsingGZIPInputStreamUnitTest.java

* Update Main.java

* Update Main.java

* Update ReadingGZIPUsingGZIPInputStreamUnitTest.java

* Update Main.java

* Update ReadingGZIPUsingGZIPInputStreamUnitTest.java

* Update Main.java

* Update ReadingGZIPUsingGZIPInputStreamUnitTest.java

* Update Main.java

core-java-modules/core-java-io-5/src/main/java/com/baeldung/usinggzipInputstream/Main.java

@@ -0,0 +1,73 @@
+package com.baeldung.usinggzipInputstream;
+
+import java.io.*;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.function.Consumer;
+import java.util.stream.Stream;
+import java.util.zip.GZIPInputStream;
+
+import static java.util.stream.Collectors.toList;
+
+public class Main {
+    static String filePath = Objects.requireNonNull(Main.class.getClassLoader().getResource("myFile.gz")).getFile();
+
+    public static void main(String[] args) throws IOException {
+        // Test readGZipFile method
+        List<String> fileContents = readGZipFile(filePath);
+        System.out.println("Contents of GZIP file:");
+        fileContents.forEach(System.out::println);
+
+        // Test findInZipFile method
+        String searchTerm = "Line 1 content";
+        List<String> foundLines = findInZipFile(filePath, searchTerm);
+        System.out.println("Lines containing '" + searchTerm + "' in GZIP file:");
+        foundLines.forEach(System.out::println);
+
+
+        // Test useContentsOfZipFile method
+        System.out.println("Using contents of GZIP file with consumer:");
+        useContentsOfZipFile(filePath, linesStream -> {
+            linesStream.filter(line -> line.length() > 10).forEach(System.out::println);
+        });
+    }
+
+
+    public static List<String> readGZipFile(String filePath) throws IOException {
+        List<String> lines = new ArrayList<>();
+        try (InputStream inputStream = new FileInputStream(filePath);
+             GZIPInputStream gzipInputStream = new GZIPInputStream(inputStream);
+             InputStreamReader inputStreamReader = new InputStreamReader(gzipInputStream);
+             BufferedReader bufferedReader = new BufferedReader(inputStreamReader)) {
+
+            String line;
+            while ((line = bufferedReader.readLine()) != null) {
+                lines.add(line);
+            }
+        }
+
+        return lines;
+    }
+
+    public static List<String> findInZipFile(String filePath, String toFind) throws IOException {
+        try (InputStream inputStream = new FileInputStream(filePath);
+             GZIPInputStream gzipInputStream = new GZIPInputStream(inputStream);
+             InputStreamReader inputStreamReader = new InputStreamReader(gzipInputStream);
+             BufferedReader bufferedReader = new BufferedReader(inputStreamReader)) {
+
+            return bufferedReader.lines().filter(line -> line.contains(toFind)).collect(toList());
+        }
+    }
+
+    public static void useContentsOfZipFile(String filePath, Consumer<Stream<String>> consumer) throws IOException {
+        try (InputStream inputStream = new FileInputStream(filePath);
+             GZIPInputStream gzipInputStream = new GZIPInputStream(inputStream);
+             InputStreamReader inputStreamReader = new InputStreamReader(gzipInputStream);
+             BufferedReader bufferedReader = new BufferedReader(inputStreamReader)) {
+
+            consumer.accept(bufferedReader.lines());
+        }
+    }
+
+}

core-java-modules/core-java-io-5/src/test/java/com/baeldung/usinggzipInputstream/ReadingGZIPUsingGZIPInputStreamUnitTest.java

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+package com.baeldung.usinggzipInputstream;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.*;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertEquals;
+
+public class ReadingGZIPUsingGZIPInputStreamUnitTest {
+    String testFilePath = Objects.requireNonNull(ReadingGZIPUsingGZIPInputStreamUnitTest.class.getClassLoader().getResource("myFile.gz")).getFile();
+    List<String> expectedFilteredLines = Arrays.asList("Line 1 content", "Line 2 content", "Line 3 content");
+
+    @Test
+    void givenGZFile_whenUsingGZIPInputStream_thenReadLines() throws IOException {
+        try (Stream<String> lines = Main.readGZipFile(testFilePath).stream()) {
+            List<String> result = lines
+                    .filter(expectedFilteredLines::contains)
+                    .collect(Collectors.toList());
+
+            assertEquals(expectedFilteredLines, result);
+        }
+    }
+
+    @Test
+    void givenGZFile_whenUsingtestFindInZipFile_thenReadLines() throws IOException {
+        String toFind = "Line 1 content";
+
+        List<String> result = Main.findInZipFile(testFilePath, toFind);
+
+        assertEquals("Line 1 content", result.get(0));
+
+    }
+
+    @Test
+    void givenGZFile_whenUsingContentsOfZipFile_thenReadLines() throws IOException {
+        AtomicInteger count = new AtomicInteger(0);
+
+        Main.useContentsOfZipFile(testFilePath, linesStream -> {
+            linesStream.filter(line -> line.length() > 10).forEach(line -> count.incrementAndGet());
+        });
+
+        assertEquals(3, count.get());
+    }
+}