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Java 9 additions to Stream, Optional and Arrays
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‎README.md‎

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@@ -10,6 +10,7 @@ Includes all examples about Java 9 new features
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* `mvn test`
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Find more detail at:
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* [Java 9 Tutorial](https://howtoprogram.xyz/java-9-tutorial/)
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* [Set Up Eclipse, IntelliJ And NetBeans For Java 9](https://howtoprogram.xyz/2017/09/24/set-up-eclipse-intellij-and-netbeans-for-java-9/)
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* [Create Immutable Lists In Java 9 By Static Factory Methods](https://howtoprogram.xyz/2017/09/24/java-9-create-immutable-lists-static-factory-method/)
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* [Java 9 Example With Maven And JUnit 5](https://howtoprogram.xyz/2017/09/23/java-9-maven-junit-5-example/)

‎java9-language-features-examples/README.md‎

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@@ -6,6 +6,9 @@ Demonstration for:
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[Copy Streams In Java 9 With The InputStream.transferTo() Method](https://howtoprogram.xyz/2017/10/01/java-9-inputstream-transferto-copy-streams/)
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[Compare Arrays In Java 9](https://howtoprogram.xyz/2017/10/14/java-9-compare-arrays/)
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[Streams API Updates In Java 9](https://howtoprogram.xyz/2017/10/12/java-9-streams-api-updates/)
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## Prerequisites:
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* Maven >= 3.3.1

‎java9-language-features-examples/src/test/java/com/howtoprogram/java9ex/Java9ArrayCompareTest.java‎

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package com.howtoprogram.java9ex;
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import org.junit.jupiter.api.Test;
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import java.util.Arrays;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertFalse;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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public class Java9ArrayCompareTest {
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@Test
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public void arrayEqualsTest() {
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int[] existRows = {0, 1, 2, 3, 4, 5};
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int[] newRows = {3, 4, 5, 1, 2, 0};
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assertFalse(Arrays.equals(existRows, newRows));
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assertTrue(Arrays.equals(existRows, 1, 3, newRows, 3, 5));
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assertTrue(Arrays.equals(existRows, 3, 5, newRows, 0, 2));
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}
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@Test
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public void compareArraysTest() {
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int[] tomMarks = {5, 6, 7, 8, 9, 10};
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int[] aliceMarks = {5, 6, 7, 8, 9, 10};
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int[] daisyMarks = {5, 6, 7, 10, 9, 10};
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int[] maryMarks = {5, 6, 7, 8};
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assertEquals(0, Arrays.compare(tomMarks, aliceMarks));
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assertEquals(-1, Arrays.compare(tomMarks, daisyMarks));
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assertEquals(2, Arrays.compare(tomMarks, maryMarks));
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}
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@Test
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public void compareSliceArraysTest() {
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int[] tomMarks = {5, 6, 7, 8, 9, 10};
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int[] daisyMarks = {5, 6, 7, 10, 9, 10};
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int[] maryMarks = {5, 6, 7, 8};
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assertEquals(0, Arrays.compare(tomMarks, 0, 3,
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daisyMarks, 0, 3));
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assertEquals(0, Arrays.compare(tomMarks, 0, 4,
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maryMarks, 0, maryMarks.length));
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assertEquals(1, Arrays.compare(daisyMarks, 0, 4,
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maryMarks, 0, maryMarks.length));
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}
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@Test
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public void mismatchArraysTest() {
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int[] a = {1, 2, 3, 4, 5};
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int[] b = {1, 2, 3, 4, 5};
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int[] c = {1, 2, 4, 4, 5, 6};
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assertEquals(-1, Arrays.mismatch(a, b));
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assertEquals(2, Arrays.mismatch(a, c));
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assertEquals(-1, Arrays.mismatch(a, 0, 2, c, 0, 2));
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assertEquals(2, Arrays.mismatch(a, 0, 3, c, 0, 3));
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//mismatch return relative index
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assertEquals(0, Arrays.mismatch(a, 2, a.length, c, 2, 5));
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}
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}

‎java9-language-features-examples/src/test/java/com/howtoprogram/java9ex/Java9NewStreamAPITest.java‎

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package com.howtoprogram.java9ex;
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import org.junit.jupiter.api.Assertions;
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import org.junit.jupiter.api.Test;
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import java.util.stream.IntStream;
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import java.util.stream.Stream;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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public class Java9NewStreamAPITest {
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@Test
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public void dropWhileTest() {
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Stream<Integer> stdMarks = Stream.of(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
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Stream<Integer> goodMarks = stdMarks.dropWhile(s -> s < 5);
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goodMarks.forEach(System.out::println);
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System.out.println("--------------------------------");
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Stream<Integer> givenMarks = Stream.of(1, 2, 10, 9, 5, 6, 2, 3);
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Stream<Integer> remainMarks = givenMarks.dropWhile(s -> s < 5);
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remainMarks.forEach(System.out::println);
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}
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@Test
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public void takeWhileTest() {
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Stream<Integer> stdMarks = Stream.of(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
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Stream<Integer> ngMarks = stdMarks.takeWhile(s -> s < 5);
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ngMarks.forEach(System.out::println);
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System.out.println("--------------------------------");
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Stream<Integer> givenMarks = Stream.of(1, 2, 10, 9, 5, 6, 2, 3);
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Stream<Integer> remainMarks = givenMarks.takeWhile(s -> s < 5);
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remainMarks.forEach(System.out::println);
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}
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@Test
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public void streamTest() {
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Stream.iterate(0, n -> n + 1)
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.forEach(System.out::println);
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System.out.println("--------------------------------");
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Stream.iterate(0, n -> n < 100, n -> n + 1)
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.forEach(System.out::println);
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}
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@Test
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public void ofNullableTest() {
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String username = null;
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Stream st = Stream.ofNullable(username);
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assertEquals(0, st.count());
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username ="admin";
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st = Stream.ofNullable(username);
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assertEquals(1, st.count());
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}
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}

‎java9-language-features-examples/src/test/java/com/howtoprogram/optional/Java9OptionalNewMethodsTest.java‎

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package com.howtoprogram.optional;
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import org.junit.jupiter.api.Assertions;
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import org.junit.jupiter.api.Test;
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import java.io.*;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.Optional;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertThrows;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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public class Java9OptionalNewMethodsTest {
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@Test
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public void testOptionalIfPresentOrElse() {
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List<Optional<String>> days = List.of(Optional.of("Monday"),
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Optional.of("Tuesday"),
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Optional.empty(),
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Optional.ofNullable(null),
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Optional.of("Friday"),
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Optional.of("Saturday"),
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Optional.of("Sunday")
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);
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days.stream().forEach(p -> p.ifPresentOrElse(System.out::println,
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() -> System.out.println("Day not available")));
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}
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@Test
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public void testOptionalOr() {
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List<Optional<Integer>> studentAges = List.of(Optional.of(20),
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Optional.of(21),
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Optional.empty(),
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Optional.ofNullable(null),
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Optional.of(22),
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Optional.of(18),
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Optional.of(19)
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);
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studentAges.stream().map(p -> p.or(() -> Optional.of(20)))
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.forEach(System.out::println);
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}
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@Test
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public void testOptionalStream() {
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Optional<String> maleOpt = Optional.of("Male");
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Optional<String> feMaleOpt = Optional.of("FeMale");
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Optional<String> OtherOpt = Optional.empty();
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assertEquals("Male",maleOpt.stream().findFirst().get());
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assertTrue(maleOpt.stream().count() == 1);
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assertTrue(OtherOpt.stream().count() == 0);
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}
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@Test
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public void testImmutableListOrdered() {
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List<?> coffeeList = List.of("Espresso", "Latte", "Cappuccino");
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assertEquals("Espresso", coffeeList.get(0));
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assertEquals(2, coffeeList.indexOf("Cappuccino"));
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}
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@Test
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public void testImmutableListMutableElements() {
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Map<Integer, String> numbersMap = new HashMap<>();
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numbersMap.put(1, "One");
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numbersMap.put(2, "Two");
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Map<Integer, String> currencyMap = new HashMap<>();
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currencyMap.put(100, "Hundreds");
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currencyMap.put(1000, "Thousands");
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List<Map<Integer, String>> numCurrList = List.of(numbersMap, currencyMap);
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assertEquals(2, numCurrList.get(0).size());
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//Add more elements to the mutable element of the List
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numbersMap.put(3, "Three");
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numCurrList.get(0).put(4, "Four");
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assertEquals(4, numCurrList.get(0).size());
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}
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@Test
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public void testImmutableListSerializable() throws IOException {
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List<String> drinks = List.of("Coffee", "Wine", "Fruit");
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//serialize the list
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ObjectOutputStream oos = new ObjectOutputStream(System.out);
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oos.writeObject(drinks);
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//create a list of non-serializable objects
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List<OutputStream> outputStreamList = List.of(new ByteArrayOutputStream(),
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new PrintStream(System.out));
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assertThrows(NotSerializableException.class, () -> {
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oos.writeObject(outputStreamList);
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}
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);
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}
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}

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