LinkedHashSetDemo1.java

package Advances.CollectionDemo;

// https://www.youtube.com/watch?v=z8nlH3W1sBU&list=PLmOn9nNkQxJH0qBIrtV6otI0Ep4o2q67A&index=538

/** LinkedHashSet demo 1 */
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;
import org.junit.jupiter.api.Test;

public class LinkedHashSetDemo1 {

  @Test
  public void test1() {
    /**
     * LinkedHashSet demo 1
     *
     * <p>1) LinkedHashSet is HashSet's sub class
     *
     * <p>2) maintain 2 references when adding new element : pre element and next element
     *
     * <p>3) pros : good performance in looping, adding, deletion
     *
     * <p>4) cons :
     */
    Set set = new LinkedHashSet();
    set.add(456);
    set.add(123);
    set.add(123); // only storage one "123", since HashSet is non-duplicated
    set.add("aa");
    set.add("bb");
    set.add(new Person("tim", 11));
    set.add(
        new Person(
            "tim",
            11)); // NOTE : will storage 2 "Person("tim",11)" since we haven't overwrote "equals",
                  // "hashCode" methods in Person class
    set.add(new User("ann", 20));
    set.add(
        new User(
            "ann",
            20)); // NOTE : only storage 1 "User("ann",20)" if we overwrite "equals", "hashCode"
                  // methods in User class

    Iterator iterator = set.iterator();
    while (iterator.hasNext()) {
      System.out.println(iterator.next());
    }
  }
}