add RxJava/ dev project

Author: yennanliu

dev_projects/RxJava/README.md

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+# RX Java
+
+## Ref
+- https://www.youtube.com/watch?v=7mbjhNCWqvs&list=PLZ3FH0lcV0117kiek3g-qiQDkO4ezy_Ro

dev_projects/RxJava/RxJava/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<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.yen</groupId>
+    <artifactId>RxJava</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+
+        <!--
+            rxjava
+            https://mvnrepository.com/artifact/io.reactivex/rxjava
+        -->
+        <dependency>
+            <groupId>io.reactivex</groupId>
+            <artifactId>rxjava</artifactId>
+            <version>1.3.8</version>
+        </dependency>
+
+    </dependencies>
+
+</project>

dev_projects/RxJava/RxJava/src/main/java/com/yen/Main.java

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+package com.yen;
+
+import rx.Observable;
+
+public class Main {
+    public static void main(String[] args) {
+
+        System.out.println("Hello world!");
+
+        /** part 1
+         *
+         *  https://youtu.be/7mbjhNCWqvs?si=nuGVikk2eSXVRqUE
+         */
+        Observable<String> observable = Observable.create(emitter -> {
+            emitter.onNext("click on 1");
+            emitter.onNext("click on 2");
+            emitter.onNext("click on 3");
+        });
+
+        observable.subscribe(item -> {
+            System.out.println(item);
+        }, throwable -> {
+            System.out.println(throwable.getMessage());
+        }, () -> {
+            System.out.println("op complete !");
+        });
+
+    }
+
+}

dev_projects/be_scratch/ BeScratch/src/main/java/com/yen/dev/test1.java

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+package com.yen.dev;
+
+public class test1 {
+    public static void main(String[] args) {
+        System.out.println(123);
+    }
+}