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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