practice34-ggang9

src/main/java/Practice/Chapter3/ArrayPractice.java

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+package Practice.Chapter3;
+
+public class ArrayPractice {
+    public static void main(String[] args) {
+        int[] odds = {1, 3, 5, 7, 9};
+        String[] weeks = {"월", "화", "수", "목", "금", "토", "일"};
+
+        weeks = new String[7];
+        weeks[0] = "월";
+        weeks[1] = "화";
+        weeks[2] = "수";
+        weeks[3] = "목";
+        weeks[4] = "금";
+        weeks[5] = "토";
+        weeks[6] = "일";
+
+        System.out.println(weeks[3]);
+
+    }
+}

src/main/java/Practice/Chapter3/BooleanPractice.java

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+package Practice.Chapter3;
+
+public class BooleanPractice {
+    public static void main(String[] args) {
+        boolean isSuccess = true;
+        boolean isTest = false;
+
+        int base = 180;
+        int height = 185;
+        boolean isTall = height > base;
+        if (isTall) {
+            System.out.println("키 큼");
+        }
+    }
+
+
+
+
+
+}

src/main/java/Practice/Chapter3/CharPractice.java

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+package Practice.Chapter3;
+
+public class CharPractice {
+    public static void main(String[] args) {
+        char a1 = 'a';  // 문자로 표현
+        char a2 = 97;  // 아스키코드로 표현
+        char a3 = '\u0061';  // 유니코드로 표현
+
+        System.out.println(a1);  // a 출력
+        System.out.println(a2);  // a 출력
+        System.out.println(a3);  // a 출력
+
+    }
+}

src/main/java/Practice/Chapter3/FinalPractice.java

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+package Practice.Chapter3;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+
+public class FinalPractice {
+    public static void main(String[] args) {
+        String num = "123";
+        int n = Integer.parseInt(num);
+        System.out.println(n);  // 123 출력
+
+        String num1 = String.valueOf(n);
+        String num2 = Integer.toString(n);
+
+        final int n1 = 123;  // final 로 설정하면 값을 바꿀수 없다.
+        final ArrayList<String> a = new ArrayList<>(Arrays.asList("a", "b"));
+
+
+
+
+
+    }
+
+}

src/main/java/Practice/Chapter3/ListPractice.java

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+package Practice.Chapter3;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+
+public class ListPractice {
+    public static void main(String[] args) {
+        ArrayList pitches = new ArrayList();
+        pitches.add("138");
+        pitches.add("129");
+        pitches.add("142");
+
+        pitches.add(0, "133");    // 첫번째 위치에 133 삽입.
+        pitches.add(1, "133");
+
+        System.out.println(pitches.size());
+        System.out.println(pitches.remove("129"));
+
+        ArrayList<String> pitches1 = new ArrayList<>();  // 선호되는 방식
+        pitches1.add("138");
+        pitches1.add("129");
+
+        String one = pitches1.get(0);  // 형 변환이 필요없다.
+        String two = pitches1.get(1);  // 형 변환이 필요없다.
+
+        String[] data = {"138", "129", "142"};  // 이미 투구수 데이터 배열이 있다.
+        ArrayList<String> pitches2 = new ArrayList<>(Arrays.asList(data));
+        System.out.println(pitches2);  // [138, 129, 142] 출력
+
+
+    }
+}

src/main/java/Practice/Chapter3/MapPractice.java

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+package Practice.Chapter3;
+
+import java.util.HashMap;
+
+public class MapPractice {
+
+    public static void main(String[] args) {
+        HashMap<String, String> map = new HashMap<>();
+        map.put("people", "사람");
+        map.put("baseball", "야구");
+
+        System.out.println(map.get("people"));  // "사람" 출력
+        System.out.println(map.containsKey("people"));  // true 출력
+        System.out.println(map.remove("people"));  // "사람" 출력
+        System.out.println(map.size());
+        System.out.println(map.keySet());  // [baseball, people] 출력
+
+
+
+
+    }
+}

src/main/java/Practice/Chapter3/NumberPractice.java

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+package Practice.Chapter3;
+
+public class NumberPractice {
+    public static void main(String[] args) {
+        int age = 10;
+        long countOfStar = 8764827384923849L;
+
+        float pi = 3.14F;
+        double morePi = 3.14159265358979323846;
+
+        int a = 10;
+        int b = 5;
+        System.out.println(a+b);
+        System.out.println(a-b);
+        System.out.println(a*b);
+        System.out.println(a/b);
+
+        int i = 0;
+        int j = 10;
+        i++;
+        j--;
+
+        System.out.println(i);  // 1 출력
+        System.out.println(j);  // 9 출력
+
+    }
+
+}

src/main/java/Practice/Chapter3/SetPractice.java

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+package Practice.Chapter3;
+
+import java.util.Arrays;
+import java.util.HashSet;
+
+public class SetPractice {
+    public static void main(String[] args) {
+
+        HashSet<String> set = new HashSet<>(Arrays.asList("H", "e", "l", "l", "o"));
+        System.out.println(set);  //  [e, H, l, o] 출력
+
+        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));
+
+        HashSet<Integer> intersection = new HashSet<>(s1);  // s1으로 intersection 생성
+        intersection.retainAll(s2);  // 교집합 수행
+        System.out.println(intersection);  // [4, 5, 6] 출력
+
+        HashSet<Integer> union = new HashSet<>(s1);  // s1으로 union 생성
+        union.addAll(s2); // 합집합 수행
+        System.out.println(union);  // [1, 2, 3, 4, 5, 6, 7, 8, 9] 출력
+
+        HashSet<Integer> substract = new HashSet<>(s1);  // s1으로 substract 생성
+        substract.removeAll(s2); // 차집합 수행
+        System.out.println(substract);  // [1, 2, 3] 출력
+    }
+
+
+}

src/main/java/Practice/Chapter3/StringBufferPractice.java

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+package Practice.Chapter3;
+
+public class StringBufferPractice {
+    public static void main(String[] args) {
+        StringBuffer sb = new StringBuffer();  // StringBuffer 객체 sb 생성
+        sb.append("hello");
+        sb.append(" ");
+        sb.append("jump to java");
+        String result = sb.toString();
+        System.out.println(result);  // "hello jump to java" 출력
+
+        StringBuffer sb1 = new StringBuffer();
+        sb1.append("jump to java");
+        sb1.insert(0, "hello ");
+        System.out.println(sb1.toString());
+
+
+
+    }
+
+}

src/main/java/Practice/Chapter3/StringPractice.java

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+package Practice.Chapter3;
+
+public class StringPractice {
+
+    public static void main(String[] args) {
+
+//    String a = "Happy Java";
+        String b = "a";
+        String c = "123";
+
+        boolean result = true;
+        char a = 'A';
+        int i = 100000;
+
+        String a1 = "hello";
+        String b1 = "java";
+        String c1 = "hello";
+        System.out.println(a1.equals(b1)); // false 출력
+        System.out.println(a1.equals(c1)); // true 출력
+
+        String a2 = "hello";
+        String b2 = new String("hello");
+        System.out.println(a2.equals(b2));  // true
+        System.out.println(a2 == b2);  // false
+
+        String a3 = "Hello Java";
+        System.out.println(a3.indexOf("Java"));  // 6 출력
+
+        String a4 = "Hello Java";
+        System.out.println(a4.charAt(6));  // "J" 출력
+
+        String a5 = "Hello Java";
+        System.out.println(a5.replaceAll("Java", "World"));  // Hello World 출력
+
+        String a6 = "a:b:c:d";
+        String[] result1 = a6.split(":");  // result는 {"a", "b", "c", "d"}
+
+
+    }
+
+
+}

src/main/java/Practice/Chapter4/ForEachPractice.java

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+package Practice.Chapter4;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+
+public class ForEachPractice {
+    public static void main(String[] args) {
+        String[] numbers = {"one", "two", "three"};
+        for(String number: numbers) {
+            System.out.println(number);
+        }
+
+
+        ArrayList<String> numbers2 = new ArrayList<>(Arrays.asList("one", "two", "three"));
+        for (String number : numbers2) {
+            System.out.println(number);
+        }
+    }
+}

src/main/java/Practice/Chapter4/ForPractice.java

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+package Practice.Chapter4;
+
+public class ForPractice {
+    public static void main(String[] args) {
+        String[] numbers = {"one", "two", "three"};
+        for(int i=0; i<numbers.length; i++) {
+            System.out.println(numbers[i]);
+        }
+
+        int[] marks = {90, 25, 67, 45, 80};
+        for(int i=0; i<marks.length; i++) {
+            if (marks[i] >= 60) {
+                System.out.println((i+1)+"번 학생은 합격입니다.");
+            }else {
+                System.out.println((i+1)+"번 학생은 불합격입니다.");
+            }
+        }
+
+        int[] marks1 = {90, 25, 67, 45, 80};
+        for(int i=0; i<marks1.length; i++) {
+            if (marks1[i] < 60) {
+                continue;  // 조건문으로 돌아간다.
+            }
+            System.out.println((i+1)+"번 학생 축하합니다. 합격입니다.");
+        }
+
+    }
+}

src/main/java/Practice/Chapter4/IfPractice.java

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+package Practice.Chapter4;
+
+import java.util.ArrayList;
+
+public class IfPractice {
+    public static void main(String[] args) {
+        boolean money = true;
+        if (money) {
+            System.out.println("택시를 타고 가라");
+        }else {
+            System.out.println("걸어가라");
+        }
+
+        int x = 3;
+        int y = 2;
+        System.out.println(x > y);
+
+        int money1 = 2000;
+        if (money1 >= 3000) {
+            System.out.println("택시를 타고 가라");
+        }else {
+            System.out.println("걸어가라");
+        }
+
+        int money2 = 2000;
+        boolean hasCard = true;
+
+        if (money2 >=3000 || hasCard) {
+            System.out.println("택시를 타고 가라");
+        } else {
+            System.out.println("걸어가라");
+        }
+
+        ArrayList<String> pocket = new ArrayList<String>();
+        pocket.add("paper");
+        pocket.add("handphone");
+        pocket.add("money");
+
+        if (pocket.contains("money")) {
+            System.out.println("택시를 타고 가라");
+        }else {
+            System.out.println("걸어가라");
+        }
+
+
+        boolean hasCard2 = true;
+        ArrayList<String> pocket2 = new ArrayList<String>();
+        pocket2.add("paper");
+        pocket2.add("handphone");
+
+        if (pocket2.contains("money")) {
+            System.out.println("택시를 타고 가라");
+        }else if(hasCard2) {
+            System.out.println("택시를 타고 가라");
+        }else {
+            System.out.println("걸어가라");
+        }
+
+
+
+    }
+}