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hemantsonu20hemantsonu20
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set map and list factory examples added
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‎.gitignore

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2020

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# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
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hs_err_pid*
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/target/

‎pom.xml

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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>com.github.hemantsonu20</groupId>
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<artifactId>java-9-features</artifactId>
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<version>0.0.1-SNAPSHOT</version>
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<properties>
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<maven.compiler.source>1.9</maven.compiler.source>
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<maven.compiler.target>1.9</maven.compiler.target>
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</properties>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<version>3.7.0</version>
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<configuration>
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<source>1.9</source>
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<target>1.9</target>
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</configuration>
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</plugin>
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</plugins>
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</build>
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</project>
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‎src/main/java/com/github/hemantsonu20/java9/factory/ListFactory.java

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package com.github.hemantsonu20.java9.factory;
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import java.util.List;
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public class ListFactory {
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public static void main(String[] args) {
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of0();
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of1();
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of2();
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of10();
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ofArray();
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immutableCheck();
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noNullValue();
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duplicatesAllowedAsUsual();
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}
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private static void of0() {
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List<String> list = List.of();
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print(list);
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}
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private static void of1() {
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List<String> list = List.of("One");
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print(list);
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}
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private static void of2() {
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List<String> list = List.of("One", "Two");
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print(list);
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}
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private static void of10() {
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List<String> list = List.of("One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten");
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print(list);
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}
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private static void ofArray() {
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String[] arr = { "One", "Two" };
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List<String> list = List.of(arr);
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print(list);
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}
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private static void immutableCheck() {
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List<String> list = List.of("One", "Two");
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try {
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list.clear();
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} catch (UnsupportedOperationException e) {
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print("of factory methods create Immutable collections");
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}
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}
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private static void noNullValue() {
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try {
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List.of("One", null, "Two", null);
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} catch (NullPointerException e) {
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print("no null values are allowed in of factory methods");
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}
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}
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private static void duplicatesAllowedAsUsual() {
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List<String> list = List.of("One", "Two", "One");
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print(list);
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}
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private static void print(Object obj) {
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System.out.println(obj);
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}
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}

‎src/main/java/com/github/hemantsonu20/java9/factory/MapFactory.java

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package com.github.hemantsonu20.java9.factory;
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import java.util.Map;
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import java.util.Map.Entry;
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/**
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* There are sets of factory methods for immutable maps in {@link Map} class. It
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* has of methods for 0 to 10 size map. Also it has
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* {@link Map#ofEntries(Entry...)} method to create immutable maps from
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* {@link Entry} objects.
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*
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* @see Map#of()
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* @see Map#of(Object, Object)
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* @see Map#entry(Object, Object)
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* @see Map#ofEntries(Entry...)
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*
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* @author hemantsonu20
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*
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*/
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public class MapFactory {
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public static void main(String[] args) {
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of0();
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of1();
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of2();
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of10();
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immutableCheck();
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noNullKeyOrValue();
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noDuplicateKey();
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ofEntries();
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}
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private static void of0() {
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Map<String, Integer> map = Map.of();
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print(map);
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}
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private static void of1() {
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Map<String, Integer> map = Map.of("One", 1);
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print(map);
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}
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private static void of2() {
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Map<String, Integer> map = Map.of("One", 1, "Two", 2);
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print(map);
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}
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private static void of10() {
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Map<String, Integer> map = Map.of("One", 1, "Two", 2, "Three", 3, "Four", 4, "Five", 5, "Six", 6, "Seven", 7,
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"Eight", 8, "Nine", 9, "Ten", 10);
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print(map);
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}
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private static void immutableCheck() {
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Map<String, Integer> map = Map.of("One", 1);
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try {
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map.put("Two", 2);
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} catch (UnsupportedOperationException e) {
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print("of factory methods create Immutable collections");
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}
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}
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/**
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* {@link Map#of()} methods throw null pointer if any key or value is null
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*
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*/
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private static void noNullKeyOrValue() {
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try {
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Map.of("One", 1, null, 2);
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} catch (NullPointerException e) {
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print("no null keys are allowed in of factory methods");
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}
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try {
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Map.of("One", null);
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} catch (NullPointerException e) {
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print("no null values are allowed in of factory methods");
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}
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}
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private static void noDuplicateKey() {
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try {
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Map.of("One", 1, "One", 1);
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} catch (IllegalArgumentException e) {
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print("no duplicate keys are allowed in of factory methods");
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}
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}
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private static void ofEntries() {
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Map.Entry<String, Integer> entry1 = Map.entry("One", 1);
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Map.Entry<String, Integer> entry2 = Map.entry("Two", 2);
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Map<String, Integer> map = Map.ofEntries(entry1, entry2);
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print(map);
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}
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private static void print(Object obj) {
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System.out.println(obj);
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}
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}

‎src/main/java/com/github/hemantsonu20/java9/factory/SetFactory.java

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package com.github.hemantsonu20.java9.factory;
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import java.util.Set;
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public class SetFactory {
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public static void main(String[] args) {
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of0();
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of1();
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of2();
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of10();
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ofArray();
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immutableCheck();
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noNullValue();
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noDuplicates();
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}
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private static void of0() {
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Set<String> set = Set.of();
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print(set);
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}
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private static void of1() {
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Set<String> set = Set.of("One");
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print(set);
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}
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private static void of2() {
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Set<String> set = Set.of("One", "Two");
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print(set);
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}
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private static void of10() {
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Set<String> set = Set.of("One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten");
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print(set);
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}
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private static void ofArray() {
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String[] arr = { "One", "Two" };
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Set<String> set = Set.of(arr);
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print(set);
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}
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private static void immutableCheck() {
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Set<String> set = Set.of("One", "Two");
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try {
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set.clear();
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} catch (UnsupportedOperationException e) {
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print("of factory methods create Immutable collections");
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}
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}
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private static void noNullValue() {
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try {
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Set.of("One", null, "Two", null);
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} catch (NullPointerException e) {
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print("no null values are allowed in of factory methods");
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}
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}
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private static void noDuplicates() {
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try {
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Set.of("One", "Two", "One");
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} catch (IllegalArgumentException e) {
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print("no duplicates are allowed in of factory methods");
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}
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}
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private static void print(Object obj) {
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System.out.println(obj);
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}
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}

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