[RxJava] 2. Reactive ๊ธฐ๋ณธ ์—ฐ์‚ฐ์ž(Operator) - map, filter, reduce

Reactive Programming์—์„œ ๊ฝƒ์ด๋ผ๊ณ  ํ•  ์ˆ˜ ์žˆ๋Š” Reactive Operator์— ๋Œ€ํ•ด ์•Œ์•„๋ณด๋„๋ก ํ•˜๊ฒ ์Šต๋‹ˆ๋‹ค. ๋งŒ์•ฝ ์—ฌ๋Ÿฌ๋ถ„๋“ค์ด Java 8์„ ์‚ฌ์šฉํ•˜๊ณ  ์žˆ๋‹ค๋ฉด, ์ด๋Ÿฌํ•œ Reactive ์—ฐ์‚ฐ์ž๊ฐ€ ๋งค์šฐ ์ต์ˆ™ํ•˜์‹ค ์ˆ˜๋„ ์žˆ์Šต๋‹ˆ๋‹ค. RxJava์—์„œ๋Š” Reactive Programming์— ๋งž์ถฐ, ์ด๋Ÿฌํ•œ Reactive Operator๋ฅผ ์ œ๊ณตํ•ฉ๋‹ˆ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ์—ฌ๋Ÿฌ๋ถ„๋“ค์ด ์•„์…”์•ผํ•  ๊ฒƒ์€ ์ด๋Ÿฐ Reactive ์—ฐ์‚ฐ์ž๊ฐ€ ๋‹จ์—ฐ RxJava, Java 8์—์„œ์™€ ๊ฐ™์ด "Java"์—์„œ๋งŒ ๋ณผ ์ˆ˜ ์žˆ๋Š” ๊ฒƒ์€ ์•„๋‹™๋‹ˆ๋‹ค. Python์—์„œ๋„ Javascript์—์„œ๋„ Reactive Programming๋งŒ ์ง€์›ํ•œ๋‹ค๋ฉด ์ด๋Ÿฌํ•œ ์—ฐ์‚ฐ์ž๋Š” ์–ด๋””์„œ๋“  ๋ณผ ์ˆ˜ ์žˆ์Šต๋‹ˆ๋‹ค. ์ด๋ฒˆ ๊ธ€์—์„œ๋Š” RxJava์—์„œ Reative Operator๊ฐ€ ์–ด๋–ค์‹์œผ..