List기본 연습

기본연습

리스트에 요소를 추가하기

public class ExerciseList {

    public static void main(String[] args) {
        
        List<String> listExercise = new ArrayList<String>();
        
        listExercise.add("ABC");
        listExercise.add("D");
        listExercise.add("XYZ");

        System.out.println(listExercise);
    }
}

[ABC, D, XYZ]

---

리스트에 요소를 덮어 쓰기

import java.util.ArrayList;
import java.util.List;

public class ExerciseList {

    public static void main(String[] args) {
        
        List<String> listExercise = new ArrayList<String>();
        
        listExercise.add("ABC");
        listExercise.add("D");
        listExercise.add("XYZ");
        System.out.println("before : " + listExercise);
        
        // Overwrite index 0
        listExercise.set(0, "xxx");
        
        System.out.println("after  : " + listExercise);
    }
}

before : [ABC, D, XYZ]
after  : [xxx, D, XYZ]

---

두개의 리스트를 병합하기

mport java.util.ArrayList;
import java.util.List;

public class ExerciseList {

    public static void main(String[] args) {
        
        List<String> firstList = new ArrayList<String>();
        
        firstList.add("123");
        firstList.add("456");
        firstList.add("789");
        
        List<String> secondList = new ArrayList<String>();
        
        secondList.add("111");
        secondList.add("222");
        secondList.add("333");
        
        // firstList secondList Merge
        
        firstList.addAll(secondList);
        
        System.out.println(firstList);
        
        
        // secondList thirdList Merge Index
        List<String> thirdList = new ArrayList<String>();
        
        thirdList.add("Hello");
        thirdList.add("World");
        
        thirdList.addAll(1, secondList);
        
        System.out.println(thirdList);
    }
}

[123, 456, 789, 111, 222, 333]
[Hello, 111, 222, 333, World]

---

리스트의 사이즈를 알아보기

import java.util.ArrayList;
import java.util.List;

public class ExerciseList {

    public static void main(String[] args) {
        
        List<String> list = new ArrayList<String>();
        System.out.println(list.size());
        
        list.add("Hello");
        list.add("World");
        list.add("!!");
        System.out.println(list.size());
    }
}

0
3

---

리스트가 비어있는지 확인

mport java.util.ArrayList;
import java.util.List;

public class ExerciseList {

    public static void main(String[] args) {
        
        List<String> list = new ArrayList<String>();
        System.out.println(list.isEmpty());
        
        list.add("Hello");
        list.add("World");
        list.add("!!");
        System.out.println(list.isEmpty());
    }
}

true
false

---

리스트의 요소를 꺼내보기

import java.util.ArrayList;
import java.util.List;

public class ExerciseList {

    public static void main(String[] args) {
        
        List<String> list = new ArrayList<String>();
        
        list.add("Hello");
        list.add("World");
        list.add("!!");
        System.out.println("Print List Object : " + list);
        System.out.println("Print List index 0 : " + list.get(0));
        System.out.println("Print List index 1 : " + list.get(1));
        System.out.println("Print List index 2 : " + list.get(2));
    }
}

Print List Object : [Hello, World, !!]
Print List index 0 : Hello
Print List index 1 : World
Print List index 2 : !!

---

리스트의 요소를 순차적으로 꺼내기

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class ExerciseList {

    public static void main(String[] args) {
        
        List<String> employeesList = new ArrayList<String>();
        
        employeesList.add("David");
        employeesList.add("Bob");
        employeesList.add("Cavin");
        employeesList.add("Lucy");
        employeesList.add("Jackson");
        
        System.out.println("Iterator");
        System.out.println("--------");
        // Iterator
        for(Iterator<String> employee = employeesList.iterator(); employee.hasNext();) {
            System.out.println(employee.next());
        }
        
        // For
        System.out.println("--------");
        System.out.println("For");
        System.out.println("--------");
        for(int i = 0; i < employeesList.size(); i++) {
            System.out.println(employeesList.get(i));
        }
        
        // Range For
        System.out.println("---------");
        System.out.println("Range For");
        System.out.println("---------");
        for(String employee : employeesList) {
            System.out.println(employee);
        }
        
        // Collection Stream
        System.out.println("-----------------");
        System.out.println("Collection Stream");
        System.out.println("-----------------");
        employeesList.forEach((employee) -> {
            System.out.println(employee);
        });
    }
}

Iterator
--------
David
Bob
Cavin
Lucy
Jackson
--------
For
--------
David
Bob
Cavin
Lucy
Jackson
---------
Range For
---------
David
Bob
Cavin
Lucy
Jackson
-----------------
Collection Stream
-----------------
David
Bob
Cavin
Lucy
Jackson

---

리스트의 요소를 삭제하기

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class ExerciseList {

    public static void main(String[] args) {
        
        List<String> employeesList = new ArrayList<String>();
        
        employeesList.add("David");
        employeesList.add("Bob");
        employeesList.add("Cavin");
        employeesList.add("Lucy");
        employeesList.add("Jackson");
        
        System.out.println("List Size : " + employeesList.size());
        
        employeesList.remove(0);
        System.out.println(employeesList);
        
        System.out.println("List Size : " + employeesList.size());
    }
}

List Size : 5
[Bob, Cavin, Lucy, Jackson]
List Size : 4

---

리스트의 모든 요소를 삭제하기

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class ExerciseList {

    public static void main(String[] args) {
        
        List<String> employeesList = new ArrayList<String>();
        
        employeesList.add("David");
        employeesList.add("Bob");
        employeesList.add("Cavin");
        employeesList.add("Lucy");
        employeesList.add("Jackson");
        
        System.out.println("List Size : " + employeesList.size());
        System.out.println(employeesList);
        
        employeesList.clear();
        System.out.println("List Size : " + employeesList.size());
        System.out.println(employeesList);
    }
}

List Size : 5
[David, Bob, Cavin, Lucy, Jackson]
List Size : 0
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