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94
src/main/java/Practice/sunny/Chapter3/ArrayListPractice.java
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package Practice.sunny.Chapter3; | ||
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import java.util.ArrayList; | ||
import java.util.Arrays; | ||
import java.util.Comparator; | ||
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public class ArrayListPractice { | ||
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public static void main(String[] args) { | ||
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// Array | ||
int[] odds = {1, 3, 5, 7, 9}; | ||
String[] weeks = {"월", "화", "수", "목", "금", "토", "일"}; | ||
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// String[] weeks = new String[]; -> compile error | ||
String[] weeks2 = new String[7]; | ||
weeks2[0] = "월"; | ||
weeks2[1] = "화"; | ||
weeks2[2] = "수"; | ||
weeks2[3] = "목"; | ||
weeks2[4] = "금"; | ||
weeks2[5] = "토"; | ||
weeks2[6] = "일"; | ||
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// indexing | ||
System.out.println(weeks[3]); | ||
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// length of array | ||
for (int i = 0; i < weeks.length; i++) { | ||
System.out.println(weeks[i]); | ||
} | ||
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// ArrayIndexOutOfBoundsException | ||
// System.out.println(weeks[7]); | ||
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// ArrayList | ||
ArrayList pitches = new ArrayList(); | ||
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// add | ||
pitches.add("138"); | ||
pitches.add("129"); | ||
pitches.add("142"); | ||
pitches.add(0, "133"); | ||
pitches.add(2, "133"); | ||
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// get | ||
System.out.println(pitches.get(1)); | ||
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// size | ||
System.out.println(pitches.size()); | ||
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// contains | ||
System.out.println(pitches.contains("142")); | ||
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// remove | ||
System.out.println(pitches.remove("129")); | ||
System.out.println(pitches.remove(0)); | ||
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// Generics | ||
// ArrayList<String> pitches2 = new ArraList<String>(); | ||
ArrayList<String> pitches2 = new ArrayList<>(); | ||
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ArrayList pitches3 = new ArrayList(); | ||
pitches3.add("138"); | ||
pitches3.add("129"); | ||
String one = (String) pitches3.get(0); | ||
String two = (String) pitches3.get(1); | ||
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ArrayList<String> pitches4 = new ArrayList<>(); | ||
pitches4.add("138"); | ||
pitches4.add("129"); | ||
String three = pitches4.get(0); | ||
String four = pitches4.get(1); | ||
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// asList | ||
String[] data = {"138", "129", "142"}; | ||
ArrayList<String> pitches5 = new ArrayList<>(Arrays.asList(data)); | ||
System.out.println(pitches5); | ||
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ArrayList<String> pitches6 = new ArrayList<>(Arrays.asList("138", "129", "142")); | ||
System.out.println(pitches6); | ||
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// String.join | ||
String result = String.join(",", pitches6); | ||
System.out.println(result); | ||
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String result2 = String.join(",", data); | ||
System.out.println(result2); | ||
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// sort | ||
pitches6.sort(Comparator.naturalOrder()); | ||
System.out.println(pitches6); | ||
} | ||
} |
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src/main/java/Practice/sunny/Chapter3/CastingFinalPractice.java
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package Practice.sunny.Chapter3; | ||
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import java.util.ArrayList; | ||
import java.util.Arrays; | ||
import java.util.List; | ||
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public class CastingFinalPractice { | ||
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public static void main(String[] args) { | ||
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// String to Integer | ||
String num1 = "123"; | ||
int n1 = Integer.parseInt(num1); | ||
System.out.println(n1); | ||
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// Integer to String | ||
int n2 = 123; | ||
String num2 = "" + n2; | ||
System.out.println(num2); | ||
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int n3 = 123; | ||
String num3 = String.valueOf(n3); | ||
String num4 = Integer.toString(n3); | ||
System.out.println(num3); | ||
System.out.println(num4); | ||
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// String to Float | ||
String num5 = "123.456"; | ||
double d = Double.parseDouble(num5); | ||
System.out.println(d); | ||
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// Integer to Float | ||
int n4 = 123; | ||
double d1 = n4; | ||
System.out.println(d1); | ||
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// Float to Integer | ||
double d2 = 123.456; | ||
int n5 = (int) d2; | ||
System.out.println(n5); | ||
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// NumberFormatException Error | ||
/* | ||
String num = "123.456; | ||
int n = Integer.parseInt(num); | ||
*/ | ||
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// Final | ||
final int n6 = 123; | ||
// n6 = 456; -> Compile Error | ||
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// Final List | ||
final ArrayList<String> a = new ArrayList<>(Arrays.asList("a", "b")); | ||
// a = new ArrayList<>(Arrays.asList("c", "d")); -> Compile Error | ||
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// List.of | ||
final List<String> b = List.of("a", "b"); | ||
a.add("c"); | ||
} | ||
} |
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package Practice.sunny.Chapter3; | ||
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public class EnumPractice { | ||
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enum CoffeeType { | ||
AMERICANO, | ||
ICE_AMERICANO, | ||
CAFE_LATE | ||
} | ||
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; | ||
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public static void main(String[] args) { | ||
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System.out.println(CoffeeType.AMERICANO); | ||
System.out.println(CoffeeType.ICE_AMERICANO); | ||
System.out.println(CoffeeType.CAFE_LATE); | ||
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// for loop | ||
for (CoffeeType type : CoffeeType.values()) { | ||
System.out.println(type); | ||
} | ||
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// Why use Enum | ||
/* | ||
int countSellCoffee(int type){ | ||
... | ||
} | ||
int americano = countSellCoffee(1); | ||
int result = countSellCoffee(99); -> error | ||
int countSellCoffee(CoffeeType type){ | ||
... | ||
} | ||
int americano = countSellCoffee(CoffeeType.AMERICANO); | ||
*/ | ||
} | ||
} |
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package Practice.sunny.Chapter3; | ||
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import java.util.ArrayList; | ||
import java.util.HashMap; | ||
import java.util.List; | ||
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public class MapPractice { | ||
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public static void main(String[] args) { | ||
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// HashMap | ||
// put | ||
HashMap<String, String> map = new HashMap<>(); | ||
map.put("people", "사람"); | ||
map.put("baseball", "야구"); | ||
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// get | ||
System.out.println(map.get("people")); | ||
System.out.println(map.get("java")); | ||
System.out.println(map.getOrDefault("java", "자바")); | ||
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// containsKey | ||
System.out.println(map.containsKey("people")); | ||
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// remove | ||
System.out.println(map.remove("people")); | ||
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// size | ||
System.out.println(map.size()); | ||
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// keySet | ||
System.out.println(map.keySet()); | ||
List<String> keyList = new ArrayList<>(map.keySet()); | ||
} | ||
} |
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src/main/java/Practice/sunny/Chapter3/NumBoolPractice.java
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package Practice.sunny.Chapter3; | ||
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import java.nio.file.FileSystemNotFoundException; | ||
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public class NumBoolPractice { | ||
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public static void main(String[] args) { | ||
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// Integer | ||
int age = 10; | ||
long countOfstar = 8764827384923849L; | ||
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// Float | ||
float pi = 3.14F; | ||
double morePi = 3.14159265358979323846; | ||
double d1 = 123.4; | ||
double d2 = 1.234e2; | ||
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// Oct, Hex | ||
int octal = 023; // Decimal : 19 | ||
int hex = 0xC; // Decimal : 12 | ||
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// Add, Subtract, Multiply, Divide | ||
int a = 10; | ||
int b = 5; | ||
System.out.println(a + b); // print 15 | ||
System.out.println(a - b); // print 5 | ||
System.out.println(a * b); // print 50 | ||
System.out.println(a / b); // print 2 | ||
System.out.println(7 % 3); // print 1 | ||
System.out.println(3 % 7); // print 3 | ||
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// Increment, Decrement | ||
int i = 1; | ||
int j = 10; | ||
i++; | ||
j--; | ||
System.out.println(i); // print 1 | ||
System.out.println(j); // print 9 | ||
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i = 0; | ||
System.out.println(i++); // print 0 | ||
System.out.println(i); // print 1 | ||
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i = 0; | ||
System.out.println(++i); // print 1 | ||
System.out.println(i); // print 1 | ||
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// Boolean | ||
boolean isSuccess = true; | ||
boolean isTest = false; | ||
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// Boolean operation | ||
// 2 > 1 -> true | ||
// 1 == 2 -> false | ||
// 3 % 2 == 1 -> true | ||
// "3".equals("2") -> false | ||
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// Conditional | ||
int base = 180; | ||
int height = 185; | ||
boolean isTall = height > base; | ||
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if (isTall) { | ||
System.out.println("키가 큽니다."); // print 키가 큽니다. | ||
} | ||
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i = 3; | ||
boolean isOdd = i % 2 == 1; | ||
System.out.println(isOdd); // print true | ||
} | ||
} |
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package Practice.sunny.Chapter3; | ||
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import java.util.Arrays; | ||
import java.util.HashSet; | ||
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public class SetPractice { | ||
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public static void main(String[] args) { | ||
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// HashSet | ||
HashSet<String> set = new HashSet<>(Arrays.asList("H", "e", "l", "l", "o")); | ||
System.out.println(set); | ||
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HashSet<Integer> s1 = new HashSet<>(Arrays.asList(1, 2, 3, 4, 5, 6)); | ||
HashSet<Integer> s2 = new HashSet<>(Arrays.asList(4, 5, 6, 7, 8, 9)); | ||
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// Intersection | ||
HashSet<Integer> intersection = new HashSet<>(s1); | ||
intersection.retainAll(s2); | ||
System.out.println(intersection); | ||
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// Union | ||
HashSet<Integer> union = new HashSet<>(s1); | ||
union.addAll(s2); | ||
System.out.println(union); | ||
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// Relative Complement | ||
HashSet<Integer> subtract = new HashSet<>(s1); | ||
subtract.removeAll(s2); | ||
System.out.println(subtract); | ||
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// Add | ||
HashSet<String> set2 = new HashSet<>(); | ||
set2.add("Jump"); | ||
set2.add("to"); | ||
set2.add("Java"); | ||
System.out.println(set2); | ||
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// AddAll | ||
HashSet<String> set3 = new HashSet<>(); | ||
set3.add("Jump"); | ||
set3.addAll(Arrays.asList("To", "Java")); | ||
System.out.println(set3); | ||
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// Remove | ||
HashSet<String> set4 = new HashSet<>(); | ||
set4.remove("To"); | ||
System.out.println(set4); | ||
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} | ||
} |
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