Memory Leaks article (#2142)

* Create memory-leaks module

* Memory Leaks

* Added str.intern()

* Memory Leaks updated

guest/memory-leaks/pom.xml

@@ -0,0 +1,39 @@
+<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>
+	<groupId>com.baeldung</groupId>
+	<artifactId>memory-leaks</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+
+	<dependencies>
+		<dependency>
+			<groupId>junit</groupId>
+			<artifactId>junit</artifactId>
+			<version>4.12</version>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<resources>
+			<resource>
+				<directory>src/main/resources/</directory>
+				<excludes>
+					<exclude>**/*.java</exclude>
+				</excludes>
+			</resource>
+			<resource>
+				<directory>src/test/resources/</directory>
+			</resource>
+		</resources>
+		<plugins>
+			<plugin>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<version>3.5</version>
+				<configuration>
+					<source>1.8</source>
+					<target>1.8</target>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+</project>

guest/memory-leaks/src/test/java/com/baeldung/Key.java

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+package com.baeldung;
+
+public class Key {
+
+    public static String key;
+
+    public Key(String key) {
+        Key.key = key;
+    }
+
+}

guest/memory-leaks/src/test/java/com/baeldung/MemoryLeaksTest.java

@@ -0,0 +1,86 @@
+//package com.baeldung;
+//
+//import java.io.BufferedReader;
+//import java.io.File;
+//import java.io.IOException;
+//import java.io.InputStream;
+//import java.io.InputStreamReader;
+//import java.net.URISyntaxException;
+//import java.net.URL;
+//import java.net.URLConnection;
+//import java.nio.charset.StandardCharsets;
+//import java.nio.file.Files;
+//import java.nio.file.Paths;
+//import java.nio.file.StandardOpenOption;
+//import java.util.ArrayList;
+//import java.util.Map;
+//import java.util.Random;
+//import java.util.Scanner;
+//
+//import org.junit.FixMethodOrder;
+//import org.junit.Test;
+//import org.junit.runner.RunWith;
+//import org.junit.runners.JUnit4;
+//import org.junit.runners.MethodSorters;
+//
+//@FixMethodOrder(MethodSorters.NAME_ASCENDING)
+//@RunWith(JUnit4.class)
+//public class MemoryLeaksTest {
+
+//    private Random random = new Random();
+//    public static final ArrayList<Double> list = new ArrayList<Double>(1000000);
+//
+//    @Test(expected = OutOfMemoryError.class)
+//    public void givenStaticField_whenLotsOfOperations_thenMemoryLeak() throws InterruptedException {
+//        while (true) {
+//            int k = random.nextInt(100000);
+//            System.out.println(k);
+//            Thread.sleep(10000); //to allow GC do its job
+//            for (int i = 0; i < k; i++) {
+//                list.add(random.nextDouble());
+//            }
+//        }
+//
+//    }
+//
+//    @SuppressWarnings({ "resource" })
+//    @Test(expected = OutOfMemoryError.class)
+//    public void givenLengthString_whenIntern_thenOutOfMemory() throws IOException {
+//        String str = new Scanner(new File("src/test/resources/large.txt"), "UTF-8").useDelimiter("\\A")
+//            .next();
+//        str.intern();
+//        System.out.println("Done");
+//    }
+
+//    @Test(expected = OutOfMemoryError.class)
+//    public void givenURL_whenUnclosedStream_thenOutOfMemory() throws IOException, URISyntaxException {
+//        String str = "";
+//        URLConnection conn = new URL("http://norvig.com/big.txt").openConnection();
+//        BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream(), StandardCharsets.UTF_8));
+//        while (br.readLine() != null) {
+//            str += br.readLine();
+//        }
+//        Files.write(Paths.get("src/main/resources/"), str.getBytes(), StandardOpenOption.CREATE);
+//    }
+//
+//    @SuppressWarnings("unused")
+//    @Test(expected = OutOfMemoryError.class)
+//    public void givenConnection_whenUnclosed_thenOutOfMemory() throws IOException, URISyntaxException {
+//        URL url = new URL("ftp://speedtest.tele2.net");
+//        URLConnection urlc = url.openConnection();
+//        InputStream is = urlc.getInputStream();
+//        String str = "";
+//        while (true) {
+//            str += is.toString()
+//                .intern();
+//        }
+//    }
+//
+//    @Test(expected = OutOfMemoryError.class)
+//    public void givenMap_whenNoEqualsNoHashCodeMethods_thenOutOfMemory() throws IOException, URISyntaxException {
+//        Map<Object, Object> map = System.getProperties();
+//        while (true) {
+//            map.put(new Key("key"), "value");
+//        }
+//    }
+//}