ListDemo1.java

package Advances.CollectionDemo;

// https://www.youtube.com/watch?v=Y6U0PnnjNRs&list=PLmOn9nNkQxJH0qBIrtV6otI0Ep4o2q67A&index=527
// https://www.youtube.com/watch?v=iQnIoSjxdeo&list=PLmOn9nNkQxJH0qBIrtV6otI0Ep4o2q67A&index=528
// https://www.youtube.com/watch?v=CTvv2SEH3l4&list=PLmOn9nNkQxJH0qBIrtV6otI0Ep4o2q67A&index=529
// https://www.youtube.com/watch?v=KptmLcdTECg&list=PLmOn9nNkQxJH0qBIrtV6otI0Ep4o2q67A&index=531

/** List demo 1 */
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.junit.jupiter.api.Test;

/**
 * List Demo1 |-- List interface : storage ordering, duplicated record -> "dynamic" array |---
 * ArrayList : LinkedList, Vector
 *
 * <p>1) List is Collection's sub interface 2) we usually use this (List) in java 3) List has
 * ordering elements, duplicated elements (every element has its order index) 4) we can get element
 * from List via index 5) common implemented class : - ArrayList - LinkedList - Vector 6) ArrayList
 * VS LinkedList VS Vector ? same : all of the 3 classes are list interface's implementation. Can
 * storage ordering, duplicated records difference : - ArrayList : main implementation from List
 * interface. thread non safety, high efficiency. low level : use Object[] for storage - LinkedList
 * : use case : frequent add, delete op. LinkedList has better performance than ArrayList. Under the
 * hood : use dequeue (double direction queue) for storage - Vector : `aged` (old) implemented class
 * from List interface (since JDK 1). thread safety, low efficiency. Under the hood : use Object[]
 * for storage
 *
 * <p>7) ArrayList in JDK 8 - ArrayList List = new ArrayList() // under the hood Object[]
 * elementData init as {}, not create array yet
 *
 * <p>8) Summary : - JDK 7 : ArrayList instantiation is similar to "singlet lazy Eager
 * initialization" (餓漢式) - JDK 8 : ArrayList instantiation is similar to "singlet lazy
 * initialization" (懶漢式) - delay class creation, save resources
 */
public class ListDemo1 {
  /** List common methods 1 */
  @Test
  public void test1() {
    ArrayList list1 = new ArrayList();

    // add
    list1.add(123);
    list1.add(456);
    list1.add("aa");
    list1.add(new Person("tim", 11));
    list1.add(123);
    System.out.println(list1);

    // add(int index, object obj)
    list1.add(list1);

    // addAll
    List list2 = Arrays.asList(1, 2, 3);
    list1.addAll(list2);
    System.out.println(list1);

    // get
    System.out.println(list1.get(1));
  }

  @Test
  public void test2() {
    /** List common methods 2 */
    ArrayList list1 = new ArrayList();

    list1.add(123);
    list1.add(456);
    list1.add("aa");
    list1.add(new Person("tim", 11));
    list1.add(123);

    // indexOf
    System.out.println(list1.indexOf(123));

    // lastIndexOf
    System.out.println(list1.lastIndexOf(123));

    // remove
    Object obj = list1.remove(1);
    System.out.println("obj = " + obj);
    System.out.println(list1);

    // set
    list1.set(0, "zz");
    System.out.println(list1);

    // subList
    List list1_ = list1.subList(1, 3);
    System.out.println(list1_);
  }
}