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updated docs;
Java 13 examples;
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‎README.md

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@@ -19,15 +19,25 @@ A project to explore more about the new features of Java 8, 9, ...
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* Java 10
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* Process API
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* Collections improvements
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* Switch expression (preview)
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* Application Class-Data Sharing
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* var
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* Java 11
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* Http Client (incubator)
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* Java 12
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* Switch expression (preview 2)
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* Switch expression (preview 1)
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* Compact Number Format
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* Collectors improvements
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* CompletableFuture improvements
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* CDS enable by default
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* New GC and improvements
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* Java 13
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* Switch expression (preview 2)
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* Text blocks
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* String API updates
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* NIO updates
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* Socket and ServerSocket reimplementation (Project Loom)
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* Dynamic CDS Archives
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* ZGC: Uncommit Unused Memory

‎java-10/README.md

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# Java 10
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## JEPs
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* [310](https://openjdk.java.net/jeps/310) - Application Class-Data Sharing

‎java-11/README.md

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# Java 11
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## Links
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* [Oracle's Z GC](https://wiki.openjdk.java.net/display/zgc/Main)

‎java-12/README.md

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* [12](https://openjdk.java.net/jeps/12) - Preview language and VM features
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* [325](http://openjdk.java.net/jeps/325) - Switch expressions (preview)
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* [341](http://openjdk.java.net/jeps/341) - Default CDS Archives
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* [189](http://openjdk.java.net/jeps/189) - Low-Pause-Time GC
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* [189](http://openjdk.java.net/jeps/189) - Low-Pause-Time GC (experimental)
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* [344](http://openjdk.java.net/jeps/344) - Abortable mixed collections for G1
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* [345](http://openjdk.java.net/jeps/346) - Promptly return unused memory from G1
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* [334](http://openjdk.java.net/jeps/334) - JVM Constants API
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* compiler plugin: 3.8.0
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* surefire and failsafe: 2.22.0
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```
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```xml
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<plugin>
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<artifactId>maven-compiler-plugin</artifactId>
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<configuration>
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## Links
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* [Java 12 Guide](https://blog.codefx.org/java/java-12-guide/)
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* [Should you adopt Java 12 or stick on Java 11?](https://blog.joda.org/2018/10/adopt-java-12-or-stick-on-11.html)
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* [Should you adopt Java 12 or stick on Java 11?](https://blog.joda.org/2018/10/adopt-java-12-or-stick-on-11.html)
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* [Shenandoah GC](https://wiki.openjdk.java.net/display/shenandoah/Main)

‎java-13/README.md

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# Java 13
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To run each example use: `java --enable-preview --source 13 <FileName.java>`
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## Features
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### Language
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* Switch expressions improvements
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* Changed `break` from Java 12 to `yield`
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* Text blocks
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* flag to compile: `-Xlint:text-blocks`
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* API improvements
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* String methods:
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* `stripIdent`: same operation done by the compiler to strip incidental identation from text block';
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* `translateEscapes`: same operation done by the compiler to translate escapes in strings;
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* `formatted`: shortcut to String.format '`"%s years old".formatted(42)`)
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* NIO improvements
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* Socket and ServerSocket reimplementation (alignment to [Project Loom](https://openjdk.java.net/projects/loom/))
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### JVM
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* Creating Class-Data archives For AppCDS
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* flag to java `-XX:ArchiveClassesAtExit=<FileHere.jsa>` to generate class-data on exit
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* run with it: `-XX:SharedArchiveFile=<FileHere.jsa>`
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* ZGC (Oracle's Z GC) returns unused memory to SO
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* `-XX:ZUncommitDelay=<seconds>` to set the delay in seconds
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* `-XX:SoftMaxHeapSize`: soft (won't generate OutOfMemoryError - will request more) limit to avoid the JVM to grow in memory
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## JEPs
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* [354](https://openjdk.java.net/jeps/354) - Switch expression (preview 2)
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* [355](https://openjdk.java.net/jeps/355) - Text blocks (preview)
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* [350](https://openjdk.java.net/jeps/350) - Dynamic CDS Archives
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* [351](https://openjdk.java.net/jeps/351) - ZGC: Uncommit Unused Memory
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* [353](https://openjdk.java.net/jeps/353) - Reimplement the Legacy Socket API
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## Warnings
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* Tools
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* Maven: 3.5.0
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* compiler plugin: 3.8.0
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* surefire and failsafe: 2.22.0
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* plugins using ASM (e.g. the shade plugin) will likely need to be updated as well
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```xml
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<plugin>
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<artifactId>maven-compiler-plugin</artifactId>
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<configuration>
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<release>13</release>
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<compilerArgs>
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--enable-preview
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</compilerArgs>
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</configuration>
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</plugin>
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<plugin>
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<artifactId>maven-surefire-plugin</artifactId>
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<configuration>
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<argLine>--enable-preview</argLine>
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</configuration>
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</plugin>
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<plugin>
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<artifactId>maven-failsafe-plugin</artifactId>
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<configuration>
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<argLine>--enable-preview</argLine>
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</configuration>
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</plugin>
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```
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## Links
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* [Java 13 Guide](https://blog.codefx.org/java/java-13-guide/)
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* [Switch Expression](https://blog.codefx.org/java/switch-expressions/)
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* [Text Block Guid](http://cr.openjdk.java.net/~jlaskey/Strings/TextBlocksGuide_v9.html)

‎java-13/SwitchExpressionTests.java

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/*
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* Same example from Java 12 but with syntax update.
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*/
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public class SwitchExpressionTests {
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public static void main(String ... args) {
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compatibleWithOldVersion();
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longVersion();
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shortVersion();
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switchWithReturn();
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inferringType();
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}
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public static void compatibleWithOldVersion() {
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int luckNumber = 7;
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// we can use the old syntax (case:)
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var wasLucky = switch (luckNumber) {
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// here the fall-through happens (if there is no break or return the next case will be executed)
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case 7:
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yield false;
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case 13:
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yield true;
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// here we must provide a default case (compiler checks exhaustiveness)
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default:
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throw new IllegalArgumentException("Wrong number");
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}; // switch expression needs ;
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System.out.println("\nWas I lucky? " + wasLucky);
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}
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public static void longVersion() {
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var mood = Incomes.Good;
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// arrow syntax with no fall-through (only the arrow block will be executed)
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var shouldIGo = switch (mood) {
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// accepts multiple case labels
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case Good, Regular -> {
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yield true;
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}
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case Bad -> {
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yield false;
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}
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// there is no need to use default (we covered all possible cases)
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};
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System.out.println("\nShould I go? " + shouldIGo);
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}
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public static void shortVersion() {
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var mood = Incomes.Good;
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// cool syntax with no fall-through (only the arrow block will be executed)
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var shouldIGo = switch (mood) {
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// accepts multiple case labels
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case Good, Regular -> true;
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case Bad -> false;
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// there is no need to use default (we covered all possible cases)
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};
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System.out.println("\nShould I go? " + shouldIGo);
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}
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public static void switchWithReturn() {
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var mood = Incomes.Bad;
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// used as statement (there is no assign)
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switch (mood) {
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case Good -> {
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var easy = true;
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System.out.println("\nKeep working");
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}
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case Regular, Bad -> {
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// we can now declare vars with same name (each arrow has its own scope)
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var easy = true;
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System.out.println("\nGo home");
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/*
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* we can only return inside a block and when switch
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* is used as statement
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*/
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return;
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}
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}
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}
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public static void inferringType() {
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var mood = Incomes.Good;
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// compiler infers the most specific supertype
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// of String and IllegalArgumentException = Serializable
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// Serializable whichType // we can only use its supertype
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var whichType = switch (mood) {
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case Good -> "All right";
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default -> new IllegalArgumentException("Not right");
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};
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// won't work
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// System.out.println("What is the length? " + whichType.length());
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}
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}
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enum Incomes {
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Good,
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Regular,
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Bad
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}

‎java-13/TextBlocksExample.java

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public class TextBlocksExample {
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public static void main(String[] args) {
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// Error (same line)
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// String name = """Pat Q. Smith""";
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// 3 double-quote must be followed by line terminator (new line)
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String niceJson = """
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{
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"name": "Odair Jose",
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"language": "Java"
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}"""; // same line to not append \n at the end
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System.out.println(niceJson);
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// the identation is kept based on the most left char of block (incidental white spaces)
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String html = """
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<html>
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<body>
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<p>Hello World.</p>
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</body>
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</html>
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"""; // will append a \n at the end
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System.out.println(html);
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String badJson = """
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{
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"name": "Odair Jose",
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"language": "Java"
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}""";
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System.out.println(badJson);
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}
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}

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