๋ณธ๋ฌธ ๋ฐ”๋กœ๊ฐ€๊ธฐ

ํ”„๋กœ๊ทธ๋ž˜๋ฐ ๊ณต๋ถ€/Java

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[10์ผ์ฐจ] ๋ฐฐ์—ด Array (2) Ex34 ~ Ex35 ๋ฐฐ์—ด์„ ๋Œ€์ƒ์œผ๋กœ ์ž์ฃผํ•˜๋Š” ๋ฉ”์†Œ๋“œ ๊ฒ€์ƒ‰ - boolean contains(๋ฐฐ์—ด, ๊ฒ€์ƒ‰๋Œ€์ƒ) int[] nums = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; if (contains(nums, 15)) { System.out.println("๋ฐœ๊ฒฌํ•จ"); } else { System.out.println("๋ฐœ๊ฒฌ๋ชปํ•จ"); } String[] colors = { "red", "yellow", "blue", "white", "black", "green", "purple", "gold", "silver" }; if (contains(colors, "skyblue")) { System.out.println("๋ฐœ๊ฒฌํ•จ"); } else { System.out.println("๋ฐœ๊ฒฌ๋ชป..
[9์ผ์ฐจ] ๋ฐฐ์—ด(Array), ์ •๋ ฌ ๋ฐฐ์—ด, Array - ์ฐธ์กฐํ˜• - ์ง‘ํ•ฉ ์ž๋ฃŒํ˜• > ๋ฐ์ดํ„ฐ๋ฅผ ์—ฌ๋Ÿฌ๊ฐœ ์ €์žฅํ•  ์ˆ˜ ์žˆ๋Š” ์ž๋ฃŒํ˜• - ๊ฐ™์€ ์ž๋ฃŒํ˜•์„ ์ €์žฅํ•˜๋Š” ์ง‘ํ•ฉ > ๊ฐ™์€ ์ž๋ฃŒํ˜• ๋ณ€์ˆ˜๋“ค์˜ ์ง‘ํ•ฉ - ๋ฐฉ๋“ค์€ ์—ฐ์†์œผ๋กœ ์ƒ์„ฑ(***) - ๋™์ผํ•œ ์„ฑ๊ฒฉ + ๋™์ผํ•œ ์ž๋ฃŒํ˜• > ๋ฐ์ดํ„ฐ๊ฐ€ ์—ฌ๋Ÿฌ๊ฐœ์ผ๋•Œ > ๋ฐฐ์—ด ์‚ฌ์šฉ ***** ๋ฉ”๋ชจ๋ฆฌ์˜ ๊ณต๊ฐ„์€ ํ•œ๋ฒˆ ํ• ๋‹น๋˜๋ฉด ์ ˆ๋Œ€๋กœ ๋Š˜๋ฆฌ๊ฑฐ๋‚˜ ์ค„์ผ ์ˆ˜ ์—†๋‹ค(๋ฐฐ์—ด์˜ ๊ธธ์ด๊ฐ€ ์ถฉ๋ถ„ํ•œ์ง€ ๋ฏธ๋ฆฌ ์˜ˆ์ธกํ•ด์•ผํ•จ) ***์ž๋ฐ”์˜ ์‹๋ณ„์ž๋Š” ์กฐํ•ฉํ•ด์„œ ๋งŒ๋“ค์–ด๋‚ผ ์ˆ˜ ์—†๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ๋ฐฐ์—ด์˜ ์ฒจ์ž๋Š” ๋ณ€์ˆ˜ / ์ƒ์ˆ˜๊ฐ€ ์˜ฌ ์ˆ˜ ์žˆ๋‹ค. int[] ns = new int[3]; int index = 0; ns[0] = 100; ns[index] = 100; // ๋ฐฐ์—ด์˜ ์ฒจ์ž๋Š” ๋ณ€์ˆ˜/์ƒ์ˆ˜๊ฐ€ ์˜ฌ ์ˆ˜ ์žˆ๋‹ค. ๋ฐฐ์—ด ์„ ์–ธํ•˜๊ธฐ ์ž๋ฃŒํ˜•[] ๋ฐฐ์—ด๋ช… = new ์ž๋ฃŒํ˜•[๊ธธ์ด] int[] sco..
[8์ผ์ฐจ] ๋ฐ˜๋ณต๋ฌธ for (2), while for๋ฌธ์œผ๋กœ ๋ณ„์ฐ๊ธฐ (5*5) for (int i=0; i
[7์ผ์ฐจ] ๋ฐ˜๋ณต๋ฌธ for, ๋‚œ์ˆ˜(random number) Ex31 for๋ฌธ์˜ ํ˜•ํƒœ for(์ดˆ๊ธฐ์‹; ์กฐ๊ฑด์‹; ์ฆ๊ฐ์‹) { ์‹คํ–‰๋ฌธ; x ๋ฐ˜๋ณต } ์•„๋ž˜ ์ฝ”๋“œ์˜ ์‹คํ–‰ ์ˆœ์„œ๋Š” ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค 1. ์ดˆ๊ธฐ์‹ ์‹คํ–‰: int i=1 2. ์กฐ๊ฑด์‹ ์‹คํ–‰: i ๊ธ€์ž์ˆ˜ //System.out.println(id.length()); //1.๋ช‡ํšŒ์ „? :: ์ž…๋ ฅํ•œ ์•„์ด๋””์˜ ๊ธ€์ž์ˆ˜๋งŒํผ ํšŒ์ „ //2. i์˜ ์ตœ๋Œ€๊ฐ’ > id.length() //3. charAt(id) > i ์‚ฌ์šฉ๋˜๋Š”์ง€? for (int i=0; i 'z') { System.out.println("์•„์ด๋””๊ฐ€ ์˜ฌ๋ฐ”๋ฅด์ง€ ์•Š์Šต๋‹ˆ๋‹ค. ์˜์†Œ๋ฌธ์ž๋กœ๋งŒ ์ž‘์„ฑํ•ด์ฃผ์„ธ์š”"); break; //for ํƒˆ์ถœ > ์ž˜๋ชป๋œ ๋ฌธ์ž๊ฐ€ 1๊ฐœ๋ผ๋„ ๋ฐœ๊ฒฌ๋˜๋ฉด, ๋‚˜๋จธ์ง€ ๋ฌธ์ž๋Š” ์œ ํšจ์„ฑ ๊ฒ€์‚ฌ๋ฅผ ํ•  ํ•„์š”๊ฐ€ ์—†๋‹ค. > ๋‚จ์•„์žˆ๋Š” for๋ฌธ์„ ํƒˆ์ถœํ•ด๋ผ~ } } //์˜์–ด ์†Œ๋ฌธ์ž์ธ์ง€? if..
[6์ผ์ฐจ] ์ œ์–ด๋ฌธ - ์กฐ๊ฑด๋ฌธ if, switch if๋ฌธ -์กฐ๊ฑด์„ ์ œ์‹œ ํ›„ ํ”„๋กœ๊ทธ๋žจ ํ๋ฆ„์„ ์ œ์–ดํ•œ๋‹ค. - ์กฐ๊ฑด์‹ > boolean ๊ฐ’์„ ๊ฐ€์ง„๋‹ค. - ์กฐ๊ฑด์‹์œผ๋กœ ||(or) ํ™œ์šฉํ•˜์—ฌ ์—ฌ๋Ÿฌ ์กฐ๊ฑด ๋„ฃ์„ ์ˆ˜ ์žˆ์Œ if๋ฌธ์˜ ํ˜•ํƒœ if (์กฐ๊ฑด์‹) { ์‹คํ–‰๋ฌธ; } [else if (์กฐ๊ฑด์‹) { ์‹คํ–‰๋ฌธ; }] x N [else { ์‹คํ–‰๋ฌธ; }] []: ์‚ฌ์šฉํ•ด๋„ ๋˜๊ณ , ์ƒ๋žตํ•ด๋„ ๋œ๋‹ค. x N : ํšŸ์ˆ˜ ๋งˆ์Œ๋Œ€๋กœ switch๋ฌธ, switch case๋ฌธ -์กฐ๊ฑด์œผ๋กœ ์‚ฌ์šฉ๊ฐ€๋Šฅํ•œ ์ž๋ฃŒํ˜• : ์ •์ˆ˜, ๋ฌธ์ž, ๋ฌธ์ž์—ด switch๋ฌธ์˜ ํ˜•ํƒœ switch(์กฐ๊ฑด) { case ๊ฐ’: ์‹คํ–‰๋ฌธ; break; [case ๊ฐ’: ์‹คํ–‰๋ฌธ; break;] x N [default: ์‹คํ–‰๋ฌธ; break;]} switch๋ฌธ์˜ ํ™œ์šฉ ์š”๊ตฌ์‚ฌํ•ญ] ์‚ฌ์šฉ์ž๊ฐ€ ์›”์„ ์ž…๋ ฅ > ํ•ด๋‹น ์›”์˜ ๋งˆ์ง€๋ง‰ ์ผ? int lastDate ..
[6์ผ์ฐจ] ๋‚ ์งœ ์‹œ๊ฐ„ ํ™œ์šฉ(Calendar ๋“ฑ) printf์—์„œ ์ง€์›ํ•˜๋Š” ์„ธ๊ฐ€์ง€ ํ˜•์‹๋ฌธ์ž //์š”๊ตฌ์‚ฌํ•ญ] 2023-02-08 > printf() System.out.printf("%tF\n", now); //์š”๊ตฌ์‚ฌํ•ญ] 09:22:17 (์‹œ:๋ถ„:์ดˆ) System.out.printf("%tT\n", now); //์š”๊ตฌ์‚ฌํ•ญ] ์ˆ˜์š”์ผ System.out.println(now.get(Calendar.DAY_OF_WEEK)); System.out.printf("%tA\n", now); //์š”๊ตฌ์‚ฌํ•ญ] "์ง€๊ธˆ์€ ์˜คํ›„ 2์‹œ 12๋ถ„ 53์ดˆ์ž…๋‹ˆ๋‹ค." //12H System.out.printf("์ง€๊ธˆ์€ %s %02d์‹œ %02d๋ถ„ %02d์ดˆ์ž…๋‹ˆ๋‹ค.\n" , now.get(Calendar.AM_PM) == 0 ? "์˜ค์ „" : "์˜คํ›„" , now.get(Calendar.HOUR)..
[5์ผ์ฐจ] ๋‚ ์งœ ์‹œ๊ฐ„ ์ž๋ฃŒํ˜•(Date Time) ์ž๋ฐ” ๋‚ ์งœ์‹œ๊ฐ„ ์ž๋ฃŒํ˜• 1. Date ํด๋ž˜์Šค > JDK 1.0 2. Calendar ํด๋ž˜์Šค > JDK 1.1 > ๊ฐ€์žฅ ๋Œ€์ค‘ํ™” 3. LocalDateTime, LocalDate, LocalTime ํด๋ž˜์Šค > JDK 1.8 Date ํด๋ž˜์Šค *** import๋ฌธ java.util Date date; //๋ณ€์ˆ˜ ์„ ์–ธ. ํ˜„์žฌ ์‹œ๊ฐ์„ ์ƒ์„ฑํ•ด์„œ date๋ผ๋Š” ๋ณ€์ˆ˜์— ๋‹ด์•„๋ผ Date date = new Date(); System.out.println(date); //๊ฒฐ๊ณผ : Tue Feb 07 17:18:11 KST 2023 Calendar ํด๋ž˜์Šค *** import๋ฌธ java.util //ํ˜„์žฌ ์‹œ๊ฐ„ ๊ฐ€์ ธ์˜ค๊ธฐ > ํ˜„์žฌ ์ปดํ“จํ„ฐ ์‹œ๊ณ„์˜ ์‹œ๊ฐ์„ ์–ป์–ด์˜จ๋‹ค. Calendar c1 = Calendar.getInstance(); //j..
[5์ผ์ฐจ] ๋ฉ”์†Œ๋“œ(Method), ๋ฉ”์†Œ๋“œ ์˜ค๋ฒ„๋กœ๋”ฉ, ์ง€์—ญ๋ณ€์ˆ˜(Local Variable) Ex22 ~ Ex28 ๋ฉ”์†Œ๋“œ, Method - ๋ฉ”์†Œ๋“œ(Method), ํ•จ์ˆ˜(Function), ํ”„๋กœ์‹œ์ €(Procedure), ์„œ๋ธŒ๋ฃจํ‹ด(subRutine) - ์ฝ”๋“œ์˜ ์ง‘ํ•ฉ - ๊ฐ™์€ ๋ชฉ์ ์„ ๊ฐ€์ง„ ์ฝ”๋“œ์˜ ์ง‘ํ•ฉ ๋ฉ”์†Œ๋“œ ์„ ์–ธํ•˜๊ธฐ(์œ„์น˜๋Š” class ๋‚ด๋ถ€) ์„ ์–ธ๋ถ€, ์‹œ๊ทธ๋‹ˆ์ฒ˜(sign) -public static void hello () -์ ‘๊ทผ์ง€์ •์ž ์ •์ ํ‚ค์›Œ๋“œ ๋ฐ˜ํ™˜์ž๋ฃŒํ˜• ๋ฉ”์†Œ๋“œ๋ช… ์ธ์ž๋ฆฌ์ŠคํŠธ ๊ตฌํ˜„๋ถ€(Body) - ๋ฉ”์†Œ๋“œ๊ฐ€ ํ•˜๋ ค๋Š” ์—…๋ฌด ์ฝ”๋“œ ๊ตฌํ˜„ ๋ฉ”์†Œ๋“œ ์ธ์ž๋ฆฌ์ŠคํŠธ - ์ธ์ž๋ฆฌ์ŠคํŠธ, ์ธ์ž(Arguments), ํŒŒ๋ผ๋ฏธํ„ฐ(Parameter) - ๋งค๊ฐœ๋ณ€์ˆ˜ - ๋ฉ”์†Œ๋“œ๋ฅผ ํ˜ธ์ถœํ•  ๋•Œ ๊ฐ’์„ ์ „๋‹ฌํ•ด์„œ, ๋ฉ”์†Œ๋“œ ๋‚ด์—์„œ ์‚ฌ์šฉํ•  ์ˆ˜ ์žˆ๊ฒŒ ํ•ด์ฃผ๋Š” ์—ญํ•  - ๋ฉ”์†Œ๋“œ ํ™œ์šฉ๋„๋ฅผ ๋†’์—ฌ์ค€๋‹ค. > ๋ฉ”์†Œ๋“œ ๊ฐ€์šฉ์„ฑ ***ํ˜ธ์ถœํ•  ๋•Œ ์ฃผ์˜์  1. ์ธ์ž๊ฐ’์˜ ์ˆœ์„œ 2...