ํ์ต ๋ด์ฉ
- Array (๋ฐฐ์ด) : ๊ฐ์ ์๋ฃํ ๋ณ์๋ค์ ๋ฌถ์
ํ์
์๋ฃํ ๋ฐฐ์ด๋ณ์๋ช
[] = new ์๋ฃํ[๋ฐฐ์ด์์ด์];
int Array[] = new int[5];
Array[0] = 11;
Array[1] = 22;
Array[2] = 33;
Array[3] = 44;
Array[4] = 55; //์ฒซ๋ฒ์งธ ํ๊ธฐ๋ฒ
int Array[] = {11,22,33,44,55}; //๋๋ฒ์งธ ํ๊ธฐ๋ฒ
๋์ → ์ค์ ํ → ์ ์
* ๋์ ํ ๋นํ์ฌ ๊ฐ์ Heap ์์ญ์ ์ ์ฅํ๊ณ , ์ฃผ์(address)๊ฐ์ ์์ฑํ์ฌ ๊ธฐ๋ณธ ์๋ฃํ์ด ์ ์ฅ๋๋ Stack ์์ญ์ ์ ์ฅ
์ฌ์ฉ ๋ชฉ์ - ๋ณ์ ๊ด๋ฆฌ
char cArray[] = new char[5];
cArray[0] = 'h';
cArray[1] = 'e';
cArray[2] = 'l';
cArray[3] = 'l';
cArray[4] = 'o';
char cArray1[] = {'w','o','r','l','d'};
System.out.println(""+cArray1[0]+cArray1[1]+cArray1[2]+cArray1[3]+cArray1[4]);
// ์์ชฝ์ ""์ถ๊ฐํ์ฌ ๋ฌธ์์ด๋ก ๋ฐ๊ฟ์ค์ผ world ์ถ๋ ฅ. ๋ฐ๊ฟ์ฃผ์ง ์์ผ๋ฉด ์์คํค ์ฝ๋ ์ซ์ ๋ํ ๊ฐ์ผ๋ก ์ถ๋ ฅ๋จ.
System.out.println(cArray1);
// ์บ๋ฆญํฐํ ๋ฐฐ์ด์ ์ฃผ์๊ฐ๋์ ๋ฌธ์์ถ๋ ฅ
//Wrapper class ๊ธฐ๋ณธ์๋ฃํ -> ๊ฐ์ฒดํ
- ๋ฐฐ์ด ์ด๊ธฐํ (initialize)
int Array[] = {11,22,33,44,55};
* ๋ฐฐ์ด์ ์ ์ธ๊ณผ ๋์์ ์ด๊ธฐํ (๋ถ๋ฆฌํ์ฌ ์์ฑ ์๋จ)
- ๋ฐฐ์ด ๋ณต์ฌ
int arrayNum[] = {1,2,3};
int arrayCopy[] = arrayNum; // address ๋ณต์ฌ
* arrayCopy์ ๋ฐ์ดํฐ๋ฅผ ๋ณ๊ฒฝํ๋ฉด ์๋ณธ arrayNum์ ๋ฐ์ดํฐ๋ ๋ณ๊ฒฝ๋จ. (์ฃผ์๊ฐ์ด ๊ฐ์์ก๊ธฐ ๋๋ฌธ์)
/*
๋ค์์ ์๋ฌธ์๋ฅผ ๋๋ฌธ์๋ก ๋ณ๊ฒฝํด์ ์ถ๋ ฅํ๊ณ ๋๋ฌธ์๋ฉด ์๋ฌธ์๋ก ์ถ๋ ฅํ๋ ์ฝ๋๋ฅผ ์์ฑํ๋ผ.
๋ฌธ์์ฝ๋๋ ์๋ฌธ์๊ฐ ๋๋ฌธ์๋ณด๋ค 32๋งํผ ๋ ํฌ๋ค.
ex) 'A'=65 'a'=97
*/
char ch = 'c'; //๋๋ฌธ์ ๋ณ๊ฒฝ ์ถ๋ ฅ
int ch1 = ch - 32;
System.out.println((char)ch1);
char ch3 = 'D'; //์๋ฌธ์ ๋ณ๊ฒฝ ์ถ๋ ฅ
int ch4 = ch3 + 32;
System.out.println((char)ch4);
int r = (int)(Math.random() * 5); //์ธ๋ฑ์ค number๋ฅผ 0~4๊น์ง ๋๋ค์ผ๋ก ๋ฝ์๋ธ๋ค.
int[] arrRand = {3,7,8,9,14}; //์ด์ ๊ฐ์ ๋ฐฉ๋ฒ์ผ๋ก ๋ฐฐ์ด์ ์์ ๊ท์น์ด ์์ด๋ ๋๋ค์ผ๋ก ๋ฝ์๋ผ ์ ์๋ค.
System.out.println(arrRand[r]);
- ๋ฐฐ์ด ์๋ก๋ฐ๊ฟ
๋ณ์ swap ๋ฐฉ๋ฒ๊ณผ ๋์ผํ๊ฒ ์์๋ฐฐ์ด(temp[]) ๋ฅผ ๋ง๋ค์ด์ ์ค์
int aa[] = {4,5};
int bb[] = {6,7};
int aaa[] = aa;
int bbb[] = bb;
int temp[];
temp = aaa;
aaa = bbb;
bbb= temp;
- Wrapper Class
์ผ๋ฐ ์๋ฃํ(char,int)์ ๊ฐ์ฒดํ(Class)ํ ๊ฒ
์ผ๋ฐ์ ์ผ๋ก ์ผ๋ฐ ์๋ฃํ์ ์๊ธ์ ๋๋ฌธ์๋ก ํ๊ธฐ. ( ex) boolean -> Boolean, double -> Double)
(์์ธ : int -> Integer, char -> Character ๋ก ํ๋ค์ ํ๊ธฐ)
public class MainClass {
public static void main(String[] args) {
int i = 123;
Integer in = 234;
Integer n = 234; //์ซ์ ---> ๋ฌธ์์ด
String s = n.toString(); //.toString() ํจ์
System.out.println(s);
String s1 = "1234"; //๋ฌธ์์ด ---> ์ซ์
int num = Integer.parseInt(s1); //.parseInt() ํจ์
System.out.println(num);
- Class = ๋ณ์ + ํจ์(๊ธฐ๋ฅ)
์ผ๋ฐ ์๋ฃํ๊ณผ ๋ค๋ฅธ ์ : ํจ์ ์ฌ์ฉ์ด ๊ฐ๋ฅ
- String Class
์๋๋ ์์ฃผ์ฐ๋ String Class
String str = "world";
String str2 = "worl";
str2 = str2 + "d";
System.out.println(str == str2); //์ฐ์ฐ ์ ์ str๊ณผ str2์ ๊ฐ์ ๋น๊ตํ๊ธฐ ๋๋ฌธ์ false
boolean a = str.equals(str2); // == ์ฐ์ฐ์๋ ์ฃผ์๊ฐ์ ๋น๊ต
System.out.println(a); //.equals() ํจ์๋ ๋ด์ฉ ์์ฒด๋ฅผ ๋น๊ตํ๊ธฐ๋๋ฌธ์ true
//-------------------------------------------------
String str3 = "hello world";
int index = str3.indexOf("o"); //๋ฌธ์ ์์น ํ์ ํจ์ = .indexOf("์ฐพ์๋จ์ด") = ์์์๋ถํฐ ์ฐพ์
int lastIndex = str3.lastIndexOf("o"); //.lastIndexOf("์ฐพ์๋จ์ด") = ๋ค์์๋ถํฐ ์ฐพ์
System.out.println(index); // **๋ค์์๋ถํฐ ์ฐพ์๋ ์ธ๋ฑ์ค ๋ฒํธ๋ ์์์๋ถํฐ
System.out.println(lastIndex);
//-------------------------------------------------
String str4 = "hello";
int len = str4.length(); //.length() ๊ธธ์ด
System.out.println(len);
//--------------------------------------------------
String str5 = "A*B*C*D";
String reStr = str5.replace("*",""); //.replace("๋ฐ๊ฟ๊ฐ","๋ฐ๋๊ฐ") ์์ or ์ ๊ฑฐ
System.out.println(reStr);
String str20 = "abcdexyzz";
String str21 = str20.replaceAll("[abcd]", "Y"); //.replaceAll("[๋ฐ๊ฟ๊ฐ๋ค]","๋ฐ๋๊ฐ")
System.out.println(str21);
//--------------------------------------------------
String str6 = "ํ๊ธธ๋-24-2001/12/23-์์ธ์";
String split[] = str6.split("-"); //.split("ํ ํฐ๊ฐ") ํด๋น ํ ํฐ๋ง๋ค ์คํ๋ฆฟ. ##๋ฐฐ์ด์ ์ฌ์ฉํจ
System.out.println(Arrays.toString(split)); // '-' == token
String str22 = "๋๋.๊ฒฝ๊ธฐ๋.๊ณ ์์์.์ด๊ณ .์์ต๋๋ค"; // '.'์ผ๋ก ์คํ๋ฆฟํ๋ ค๋ฉด ์์ ์ญ์ฌ๋์ฌ 2๋ฒ or ๋๊ดํธ ๊ฐ์ธ์ฃผ๊ธฐ
String split1[] = str22.split("\\.");
System.out.println(Arrays.toString(split1));
//--------------------------------------------------
String str7 = "์๋
๋ฐ๊ฐ์์ ๊ฑด๊ฐํด์";
String subStr = str7.substring(0,2); //.substring(์์๋ฌธ์์์น ~ ๋๋ฌธ์์์น+1)
System.out.println(subStr);
String str23 = "์ ๋ถ๊ฐ ์
ํธ๋ฆฌ์จ์ด ๊ฐ๋ฐ ์ค์ธ "
+ "ํญ์ฒด์น๋ฃ์ ‘๋ ํค๋ก๋์ฃผ(CT-P59)’์ ๋ํด "
+ "์กฐ๊ฑด๋ถ ํ๊ฐ ์น์ธ์ด ๋์ค๊ธฐ ์ด์ ์ด๋ผ๋ ์๋ฃ์ง ํ๋จ์ ๋ฐ๋ผ "
+ "ํ์์ ํฌ์ฌํ ์ ์๋ค๊ณ ๋ฐํ๋ค.";
String subStr2 = str23.substring(23, 36);
System.out.println(subStr2);
//--------------------------------------------------
String str8 = "hello";
String upStr = str8.toUpperCase(); //.toUpperCase() ์๋ฌธ์ -> ๋๋ฌธ์,
System.out.println(upStr);
String str9 = "WORLD";
String lowStr = str9.toLowerCase(); //.toLowerCase() ๋๋ฌธ์ -> ์๋ฌธ์
System.out.println(lowStr);
//--------------------------------------------------
String str10 = " java java java "; //.trim() ๋ฌธ์์ด ๋งจ์,๋ค์ ๊ณต๋ฐฑ ์ญ์
String trimStr = str10.trim(); // ex) ํฌํธ์ฌ์ดํธ ๊ฒ์์ฐฝ, ๋ก๊ทธ์ธ์ฐฝ์์ ๋ง์ด ์ฌ์ฉ
System.out.println(trimStr);
//--------------------------------------------------
String str11 = "๊ฐ๋๋ค๋ผ๋ง";
char c = str11.charAt(1); //.charAt(์ธ๋ฑ์ค๋ฒํธ) Index ์ซ์ ์์น์ ๋ฌธ์ ์ถ๋ ฅ
System.out.println(c);
//--------------------------------------------------
String str12 = "์์ธ์ ๋งํฌ๊ตฌ ์๊ต๋";
boolean b1 = str12.contains("๋งํฌ"); //.contains("๋ฌธ์์ด") ๋ฌธ์์ด ์ ๋ฌด
System.out.println(b1); // ์๋ฃํ boolean์ ์ฌ์ฉํ์ฌ true, false ๊ฐ์ผ๋ก ๋์ด
- ํจ์
๋์ค๋ ๊ฐ = ํจ์๋ช (๋ค์ด๊ฐ๋ ๊ฐ)
- 2์ฐจ์ ๋ฐฐ์ด
int Array[][] = new int[3][4]; //์ฒ์ ํฌ๊ธฐ๋ฅผ ์ ํ ๋ 0๋ถํฐ๊ฐ ์๋๋ผ 1๋ถํฐ
//ex)3 x 4 = 12
int Array[][] = {
{1,2,3,4},
{5,6,7,8},
{9,10,11,12}
};
int Array3[][] = new int [3][];
int Array01[] = {1,2,3,4}; //๋ค๋ฅธ 1์ฐจ์ ๋ฐฐ์ด์ 2์ฐจ์ ๋ฐฐ์ด ์์ ๋ฃ์ ์ ์๋ค.
int Array02[] = {5,6,7};
int Array03[] = {8,9};
Array3[0] = Array01;
Array3[1] = Array02;
Array3[2] = Array03;
int Array[][] = { {1, 2, 3},
{4, 5, 6} };
System.out.println(Array.length); //๊ฒฐ๊ณผ:2 //2์ฐจ์๋ฐฐ์ด์ ์๋ถ๋ถ ๊ธธ์ด
System.out.println(Array[0].length); //๊ฒฐ๊ณผ:3 //2์ฐจ์๋ฐฐ์ด์ ๋ท๋ถ๋ถ ๊ธธ์ด
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